Stiffening plate removal / reinstallation
 

I'm in the process of investigating a potential new oil leak, and looking at the necessity of removing the stiffening plate to see where the oil is coming from. I know I have weeping power steering lines, which I intend to replace over the Thanksgiving weekend. I have also seen what appears to be oil on the ground, dripping from the front opening in the stiffening plate. What I'm curious about is, could this fluid dripping from this front opening simply be old oil (from previous oil leaks which I fixed), being mixed with ATF from my power steering lines, since the foam on top of the stiffening plate can hold quite a bit of oil itself?

Now my question: I understand the bolts for the stiffening plate are one-time-use, torque to yield bolts. Should I also buy new nuts for these bolts?

Any advice / tips on removal and replacement of the stiffening plate is greatly appreciated. :thumbup:

EDIT: Please only feedback if you've replaced the bolts / nuts for your stiffening plate. I understand this is a matter of personal preference, and have no desire whatsoever to re-start the argument of whether this is necessary. Having worked in the plant where my X was built for nearly 15 years, I have my own opinion on the matter, and feel no obligation to argue the point. Thanks.

I would be more than interested to hear your opinion on this Gary - even if it means using different bolts and nuts on reassembly (i.e. Replacing with non one time use units)

That prediction that made you do that edit, is spot on. :D

It is only the bolts that are supposed to strech when tightened to torque spec. not the nuts. So i would assume that you could re-use the nuts.
That been said, if i were convinced that i needed to replace the bolts, i would go all the way and replace the nuts too.

When you remove & replace the plate, you will notice that there isn't much space to get your tools in place. But with a little fidgeting it is a relatively easy task.
Make sure you have enough working space under the car to loosen the old and tighten the new bolts with quite a bit of torque. (stage 1: 56 Nm, stage 2: +90 degrees)

Edit:
I almost forgot.. If you find that pesky oil leak, please let us know where it was.
I have that same oil drip from the front of my pan. :)

RB, the car was designed with TTY bolts for a reason. I'm not privy to the design reasoning for this, nor do I wish to be. I'm an electrical engineer by degree, not a mechanical engineer, so such topics are beyond my education and experience.

I have no problem replacing all 6 bolts and nuts, and I'm only really curious about whether the nuts should be replaced as well.

DISCLAIMER: Opinions are always welcome. Flames > /dev/null :rofl:

I have found that a short stubby 16mm wrench works best for removing the stiffening plate.

:thumbup::thumbup::thumbup:

I use an offset box end wrench to get the nuts off. It's long enough that I can wedge it against something and just remove the bolts with a ratchet.

I have done this twice. A second set of hands to hold the lower wrench is the issue as the bolt faces upwards (nut on top of the plate). If you use a long ratchet handle it is real easy. Replacement is a challenge as you need to hold 23# of plate up as you install the first one. Hence the second set of arms/hands solution.

I voted to replace both nuts and bolts.

Oil leak will be Alt/Oil filter housing and P/S hoses. God help you if it is the oil pan too.

I'm in agreement Gary for sure - I would replace the nuts and bolts when tightening the stiffening plate, pretty sure when my front suspension was replaced the guy re-used them and I've had the slightest bit of shimmy ever since -

And I also agree with Stephen, hoping its just your PS hoses but didn't you say you did your OFHG last year? If not, that's probably it - and God help you, like he said, if its the oil pan

I did the OFHG and VCG about 2 years ago, and from what I can see from underneath (without the stiffening plate removed), the oil isn't coming from either of those places. I intend to fix the weeping PS lines first and see if the spots on the driveway stop appearing. Back when I had oil leaks before, I'm sure a lot of oil collected in the foam on top of the stiffening plate. I'm hoping this time it's a case of PS fluid making it way onto the plate and mixing with the old oil, then dripping from the front hole in the plate.

Does the oil that is dripping now smell like PS or is it mixed with actual engine oil leak?

And jesus those stiffening plate bolts went through the roof - even with discount about $14 per bolt, the nuts are cheap at $1.50 apiece I would definitely do those lol and do it right

If the block and under parts were not cleaned off after all the work was done you can count on any leak will refresh the gunk and bleed oil residue all over. Solution brake clean buy 4 cans when you pull the plate.
There are two versions of this plate and depending on your assembly date yours is either nice shiny aluminum or black painted steel.
Some time in 2003 they switched.

I'm about to change my front diff fluid and so the plate has to come off. It's going to cost me nearly $200 to get new BMW OEM bolts, by the time I figure in the exchange rate and the freight. :yikes:

I'm looking at generic zinc or nickel plated M10 x 1.5 x 55mm grade 10.9 bolts locally and can get six of them for about $20. While I REALLY want to replace these bolts and REALLY want to OEM bolts, each of those two "REALLY" desires is worth about $50, meaning I'd pay about $100 to replace them.

But $200....? :confused:

There is nothing special about the bolts that I know, or that I know could be possible. Just bolts. M10 x 1.5 x 55mm class (not grade) 10.9. I'm assuming you got the numbers right there, I did not double check. They are not in any special shape to work with the TTY application here, unlike some TTY bolts.

Related to the nuts question - in a normal specially made TTY bolt, there would be a narrowed section that is purposely designed to yield first, leaving the actual thread-nut interface below yield stress. These BMW bolts are not like that, they're just regular bolts, with no narrowed stem. So it is likely that the nuts will have yielded (plastically deformed). So if you care about stuff like that and are replacing the bolts, it does make sense to replace the nuts as well. Both nuts and bolts are regular hardware (specs above).

I re-use mine carefully without worry. If you do re-use them the main thing is to definitely NOT follow the same torque procedure that is used for new hardware - you will be will be pushing deeper into the plastic deformation zone, closer to the failure point.

Also, my understanding is that the 4.4 engines are way tougher access-wise than the 3.0. I had no problems at all on my 3.0.

Loc-tite

Yeah, nah. The torque to yield thing isn't about how tight the bolt is in order to stop it coming off, it's about how much clamping force is in play holding the plate in place. Loc-tite has no role to play here... in fact using Loc-tite would alter (lower) the torque spec that would be needed to achieve the correct bolt stretch.

But yeah, it would stop it coming undone. :thumbup:

In a Aussie world with import costs beyond reason, I would choose to use grade 8 (8.8) bolts, lock washers and nuts that were of stainless config and torque that sucker down. This solution will provide a level of clamping power within engineering acceptable ranges to ensure your safe and there is no flex in high load conditions.

Go for it.

Ugh if only we could use VW subframe bolts, this one is too long though at 105mm

https://deutscheautoparts.com/n-908-235-01.html

Did this twice, once by myself and then on Stephens (pan envy...mine was stainless) and its easier with 2 people of course but also helps if your a contortionist, at least it did for some of angles i needed to get into.

The tools needed were nothing special, couple box wrenches and sockets and a lot of patience, and of course if you havent figured it out that plate isnt lite. When doing it myself I wasnt thinking it and it landed square on my chest and neck.

Also, to your question I bought new nuts...the cost was immaterial and was just right thing to do.

While I generally agree with what you're saying here, there are some specific issues that I'll point out for anyone who might do this. (again, I just re-use mine, but I feel knowledgeable enough to do it carefully; others might not)

Grade 8 is not the same as (8.8). Grade 8 is used for rating SAE bolts. The equivalent rating for Metric would be Class 10.9. "Class" for Metric, "Grade" for SAE. Class 10.9 is what these BMW overpriced bolts are rated at. Grade 5 SAE bolts are similar in strength to Class 8.8. Grade 8 SAE ~ Class 10.9.

I would just stick with M10 10.9 bolts. And make sure you get the right thread pitch too, since that affects the actual bolt stretch that occurs when you torque or TTY them down.

Stainless - no, don't do that. Stainless will be weaker, and it seems clear BMW was concerned with a specific strength rating here. If it says 10.9 on the bolt, it will be what you want. If it does not, keep looking. Besides, unless you have one of the 1% of x5's without a perpetually oil-coated stiffening plate, you don't need to worry about corrosion.

Lock washers - I would not change anything like that (I don't recall there being lock washers on there originally). If there were any original washers, they can be re-used. Nuts and bolts, try to buy Class 10.9 ones that match in every way, but without the 700% markup.

I stand corrected for all the reasons you mentioned.

Oh no - there must have something wrong with my X5 - there's supposed to be oil on the stiffening plate? What grade should I put on there and how much? ;)

I have removed and installed the stiffing plate many times, always by myself. I have not had to use any special tools. I always replace both the nuts and bolts. As you mention there are many schools of thought, my default position is always to do as recommended by BMW in cases such as this.

I think the consensus for the 3.0L M54B30 is Shell Rotella T6, 5W40, probably about a pint or so... :bustingup

Crap...Now I have to go and buy another oil......;)

No worries, Stephen... I hear the V8's use Louisville Cardinal tears as lubricant in lieu of oil... quite an abundance of that today... :D

No no no. Oil leaks and Coolant leaks on V8 are not leaking some thing like fluids as they are really leaking $$$$.:bustingup

But then the 3.0 leaking at the Oil filter housing are leaking labor through that $9.88 gasket....

If you would be so kind as to follow up on this after doing the work that would be greatly appreciated. I have a leak from the front of the stiffening plate as well. I wanted to remove the plate and have a look but the bolt issue has prevented me from simply taking an exploratory looksee. The X is my only driver right now and I must complete the task in one sitting as it were. Thanks.

Good summary!

My go-to reference for hardware is Carroll Smith's "Nuts, Bolts, Fasteners and Plumbing" ... https://www.amazon.com/Fasteners-Plu.../dp/0879384069

It's a superb reference book.

I did the fluid maintenance a few years ago. I re-used the bolts.
Not sure why BMW said it is TTY bolt.
When looking at the bolts, they are big like wheel lugs and they looked just fine w/o any stretch marks typically seen in TTY bolts (such as head gasket bolts).

BTW, there are some repair manuals (on certain car models) that say replace the wheel lugs when changing tire. I just laugh at it.

Just relax, Saturday mechanics don't fix car for a living, so they follow the Bible to the "t". BMW mechanics tell me they re-use the bolts.

I posted the DIY below. The key thing is "relax", don't lose sleep over this TTY thingy, it is an overkill when it comes to these 6 bolts:

http://www.xoutpost.com/bmw-sav-foru...se-fluids.html

Yeah and charge for new ones

As mentioned there are two camps on this issue. IMO there is no logic for a difference of opinion and it is primarily based on the cost of the nuts/bolts compared to the 'normal' cost of bolts.

One camp, not being BMW trained mechanics or engineers whose degree had any focus on this type of issue, and, even if so, don't have the BMW engineering rationale to evaluate before making a decision, or are shade tree engineers/mechanics, or base it on their experience, conclude the BMW statement is incorrect. And the other camp.

Opinions are great but I think they should be worded as such rather than as declarative statements that imply technical expertise or that a reader is ignorant for following the BMW authored technical manual.

This is not defensive or being contrary to other opinions, I think it needs to be said every once in awhile. Best practice always follows the facts.

As bcredliner has put it there are two camps.

I am fence sitter... I bought the new bolts from BMW Parts (Well ordered them) only to remove the Protection Shield (CAREFUL IT IS HEAVY!) and proceed with maintenance, once complete I was left with no option but to reinstall the old bolts due to BMW not getting the parts in time.

Truth is, I know what torsion strengths are and I am pretty well educated in material science as my job requires this knowledge on as we work in developing new materials to aid technology development.

Simply, yes the boys at BMW know there stuff. They will have understood a wide/varied number of factors for these bolts and then decided that once removed, the deformation of the internal shaft that has been subjected to internal torque - would then change the materials torsion threshold via a set formula and then not meet the varied number of factors stated in the initial specification requirement. Hence replace.

Now.. I do not know the 'Coca-Cola Recipe' for BMW engineers factors. Also I believe the margin of tolerance built in to withstand temperatures -26c and the heat of the desert +45c well exceeds my needs of -5c to (maybe) +30c driving around London on the school run in the rain.

So, in conclusion. I reused the bolts. My requirements mean that the formula BMW engineers used far exceeds my use needs and I am not thinking about using the family wagon in the Dakar rally any time soon. So I will be fine.

IMHO, I will be fine with them. But... this is my disclaimer, refit at your own risk. I did.

I truly appreciate all the great feedback! This is exactly why I'm a member here. Such great information and dialogue, which I'd never get from folks outside this forum.

I'll be working to fix my PS leak over the weekend, then probably removing the stiffening plate to inspect for oil leaks the following weekend. I'll update this thread with my findings as the work progresses.

Question:

I may be replacing my PS reservoir hoses soon - or at least replacing the clamps. I have not looked under the car yet to see if I can replace the clamps/hoses without dropping the plate.

Can these hoses be replaced without dropping the plate?
If the plate has to be dropped, can it be unbolted at the front, but left dangling (sitting on a jack) at the front and loosened at the rear? I ask because I am a one man show and will not have access to assistance.

You can remove the entire plate on your own - it's tricky holding the nuts on the top of the plate while you loosen/tighten the bolt from underneath but it can be done.

Getting someone to hold the ring spanner on the top-side nuts makes a great difference though and they won't even get dirty hands. A wife/gf/partner/child can do it - dogs not so much. :rofl:

I had a leak from the PS low-pressure Hose where it meets the PS Pump.

I tightened the clamp a bit: This stopped the leak.

No need to drop the stiffening plate. All I did was:
- Remove the plastic shield. I posted photos in forum as there are 3-4 types of screws. Search for the photo (it is in the partial cooling overhaul thread).
- If you need more space, then drive the front up the wood ramps.

Thanks. If you "tightened the clamp", I assume that means it is a worm gear clamp and not a crimp clamp?

Edit: Scratch that, I have to assume that BMW didn't put worm gear clamps anywhere. So, that leaves me with a crimp clamp to replace?

So I am going to offer my opinion here on the stiffening plate removal/reinstallation. I have removed this plate and reinstalled it on 4 occasions using the same bolts and nuts. Once when I did the timing chain/guides and seals, another when I did the motor mounts, another when I did the sway bar upgrade and one other occasion that escapes my memory. In all cases there have been no ill effects in the reusing of the bolts and nuts. Just my 2 cents.

Correct me if wrong, but there are two types of stiffening plates. One heavy one in steel, and the one that i have in aluminum. The later one doesnt weight much at all, easy to support and get the bolts back in 😄


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Depends on how strong you are Jontezan, I am no magnus magnusson but its not as light as you would think it to be and you wouldn't want it falling on your face. Also, I have the diesel so I would be interested to find out if other models like the 4.4, etc did a different one in order to save weight. I mean... really? Its a 2200KG wagon... the odd pound aint going to matter. Like Amy Schumer, a couple of extra pounds isn't going to hurt anyone. ;)

Yes My 4.6is has the aluminum stiffening plate

http://25.media.tumblr.com/tumblr_lx...n1bho4_250.gif

My 03 3.0 has the aluminum one.

Thanks for confirming.

What torquing procedure do you use? Is the plastic deformation on the bolt threads noticeable?

CN90, since this thread is about the stiffening plate, I posted a picture with a question back at a power steering thread...

http://www.xoutpost.com/1095028-post3.html

Would you mind taking a look?

You aren't going to know if reusing the stiffing plate bolts was a good or bad idea unless the lower suspension is taxed beyond the limits of the design based on a stock suspension.

Suspension modifications increase the stress on the suspension exceeding the stock design capabilities.

However, designs are intended to exceed worst case circumstances without failure. Reusing the bolts reduces that gap. I have no idea how much but since

I have modified the suspension I don't consider reusing the bolts. If I knew why they chose that type of bolt and if a stronger bolt that would take higher torque would be better for a modified suspension I would change them out.

If you have the aluminum one, you can unbolt 5/6 bolts turn it aside and let it hang on the last bolt. I am no Samuelson either, but managed to take the plate down lying under the car. Btw in sweden we dont use any jacks 😜http://uploads.tapatalk-cdn.com/2016...e7b381f0d3.jpg


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:iagree: and that is their women.....

Its all that lovely clean Swedish air that does it for you! BTW, You are driving a BMW in Sweden? I am surprised you have not been run out of town, surely its Volvo and Saab only!? (I joke but I had a Saab and loved it).

So, there are different stiffening plates? I did some research and it seems this is the case, Also the stiffening plates have different designs in terms of the inside. Mine has two access holes and some sound insulation material on the inside which is great for nuts, bolts and washers to get lost in.

Joshdub - hahaha, dude you have to love the Schumer... did I just make you shiver again?

Happy friday y'all

Insulation is there to quell the diesel clatter.

No jacks, sure, but I hope you at least used jack stands before getting under there.

Hahaha we have plenty of volvo and saab here. My better half drives an -07 9-5 2.3 biopower, and i drive a volvo v70 for the winter. But german cars are pretty common here 😄👍


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I always use jackstands before getting under the car 😄


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Has anyone found a source for these that is not at least $9 each? I can easily find M10 1.5 10.9 Flanged Bolts for about $2-$3 dollars. Unfortunately, they are all 40, 45, 50, or 60 mm and not the OEM 55 mm size. In some of the locations, a 60 mm bolt will not interfere, but it feels like they will in one or two.

If you are saying you used 4 cans of brake cleaner to clean the stiffening plate, then I would suggest that next time, get a bottle of dawn dish washing soap. I used about 4 drops mixed in water on my caked on grimy aluminum plate. It cleaned it like a champ.

Even though on the surface the cost seems ridiculous, since I don't know why they are the BMW spec and if anything else is the same spec, I pay the price. Seems logical the BMW engineers are the experts here.

I came from an engineering school. Almost all my friends are civil, electrical, software and mechanical engineers. I had a few of the civil and mechanical engineers look over the bolts and they tell me that other than the size and the grade (10.9), there is absolutely nothing special about these bolts. They aren't even "stretch" bolts.

As I have looked around the net, I find that it is extremely difficult to find these bolts in a 55mm length with the class and flange. It seems to me the low volume is the thing that makes them expensive.

Like you (seem to be), I am also a "purist" in many ways and all of my cars are now well up in the years (my sports cars are a 88 and a 95) and if I have the need for parts, I always go to Mazda and in the case of the X5, BMW first.

But when I can find nothing special about a part such as a $35 molded hose (slight bend), or a $20 cellulose gasket, I feel like this is the time to go away from OEM because their primary goal in this case is not high quality, but to suction dollars from my pockets.

My local dealer seems especially adept at achieving this goal, having their parts sell at about 30% higher than other dealers in the area.

In this case, I read that some people prefer to get the OEM bolts, I also see that many have chosen to go with a-m or to reuse. But I have not read of any case where there was a catastrophic failure of the bolts.

I will take the vehicle out on the road a few times, if I get any indication that the car is not right, I will then look into replacing the bolts, but as I said in the other thread, with the mileage, I do believe the chances of me removing this plate again soon is not low, and a cost of $95 (out of curiosity, I decided after writing this post to check the price at the local dealer $18.65 [$111.90]) just to replace 6 seemingly non-special bolts without proof or indications from engineers I know that they MUST be replaced, I am going to join the "I'll take my chances" (for now) camp.

But as always, I do appreciate the input.

This has been discussed before.
I re-used the bolts, zero issues.
Don't overthink this or blindly follow the book.

These bolts are BIG.

BMW mechanics are dealer re-use these bolts.

My dealer does not stock these bolts. They always reuse them when removing the steel plate. I plan on reusing mine or if I lose some of them I will go to my bolt and nut store and get something close.

I've removed the plate once and re-used the bolts, and most recently I removed the plate again— I plan to re-use the bolts again. I don't care what BMW says, these are regular bolts and will likely outlive the X5.

When you torque reused bolts what target do you use? Do you still got to 42 ft lbs + 90 degree angle?

The reinforcement plate is an integral part of the suspension and is there for performance and safety.

The bolt torquing sequence in the manual is that of TTY bolts. TTY bolts should not be reused as the torquing sequence takes them to the point they begin to stretch. While they may reach torque specs when re-used they will be stretched further, causing the bolt to weaken and reducing the clamping capability.

Reading posts of many threads here and in other forums, I see pricing of the bolts driving the question of re-use, individuals having no problem with re-using the bolts posting that as verification that it is fine to re-use the bolts and folks that do not have the appropriate education to state it is not necessary to replace the bolts.

The Bentley BMW service manual clearly states that the bolts are one time use only. There is also a warning statement.

I've been tempted to re-use the bolts because of the cost but I always think of a time on the Dallas Tollway when there was an accident in front of me and I had to jerk the wheel and fly across three lanes at near 80mph. I expected I would slide into the outside barrier but I corrected and all was well. The hit would have been on my wife's side. I don't know if re-used bolts would have broken and the suspension collapsed but---

My only point is the price of the bolts is small in comparison to injuring myself, certainly a member of my family or people in other vehicles. I don't expect this will change anything. I think those seeking justification for not re-using the bolts to avoid the cost are the ones wearing blinders. At least don't let the cost be your reason for re-using them.

I think the prudent course of this discussion should be to find a source for the exact bolt from OEM or some other manufacturing source to lower the cost and end the debate.

^It's not much of a debate. Either you are okay reusing them (as MANY have), or you are not. Neither side has proof of any negative effects, other than one poster who encountered noise from the chassis, of reusing the bolts. BMW most likely recommends replacement simply because they are a part of the vehicle's structure. Much the same as them recommending replacement of all the nuts on the suspension whenever a component is replaced. Seen people reuse those too, though I do replace those as they usually come with the suspension component.

I reused, and will continue to reuse them until such time the reinforcement plate starts squeaking as some have reported, or the bolts show some visible sign of wear.

I got 42ft lbs and then did an ~75 degree angle. I used red locktite on the bolts as well just as a precaution.

I just torque em good and tight. It's just a stiffening plate, not some critical control arm.

And yeah, the cost of the bolts is the main concern for me— I don't feel like spending a bunch of money on something so non-essential, especially when the X5 (and my 540it) need other, more expensive parts. I just had to spend $160 on a new key for my 540it and like $700 to fix my X5's transfer case and front driveshaft. It's all about priorities, I guess. If the X5 was my only car then maybe I'd consider buying new bolts, but since I have several other cars, I gotta cut corners somewhere.

I am not trying to convince anyone they are making a mistake and I don't care about anyone's choice. I do think it important those asking are provided information to make an informed decision. When I learned the cost and wondered why I found information like the following two: Proper installation and use of T-T-Y Bolts - Fel-Pro Only Torque to Yield Bolts I didn't find anything in print that it doesn't matter or it is a myth. IMO opinion it is not about proof they have failed it is about the reason they can fail. Granted MANY re-use the bolts. At one time MANY believed the Earth was flat.

It is most certainly is a debate, as both sides always 'pitch' what they do and why. What gets posted in other forums are the same debate and also anecdotal and not statistically applicable.

Reused bolts can reach the torque spec. It is not about achieving torque spec it is about the lose of clamping power and a weakened fastener. BMW uses single use fasteners in places such at when the bolt threads into aluminum. What suspension fasteners does BMW state- DO NOT RE-USE?

Those considering re-use should be provided the opportunity to make a decision based on the worth of the science rather than conjecture.

Again, I couldn't care less what anyone does but I assume at least some that are re-using the bolts have not been exposed to the technical data.

----------
Disclaimer - don't try this at home.
----------

No, you can't do that. That procedure, if repeated enough times, will almost certainly break the bolt.

The Y = "yield" in TTY suggests that when installed the first time, if done properly with careful surface preparation, light oil on the threads and washer (or whatever exactly is specified for this application), the stress on the bolt will exceed the yield stress, resulting in plastic deformation (yield, permanent stretch).

My Bentley, page 310-2, says the spec is 56 Nm (41 ft-lb) + 90*. In addition to saying the fasteners should be new, it says the tightening should be done with the car on the ground and loaded, bouncing the suspension a few times before final tightening. So for those purists who want to follow specs to the letter, there it is. I can't imagine a professional mechanic getting on the ground to do this, just like (I hear) they don't actually use new bolts, and (I hear) dealers don't even stock them.

My Bentley, page 020-4, referencing DIN 267, give a general torque value for M10 10.9 as 66 Nm. They intend that as a default, safe value for bolts with otherwise unspecified torque values. So if you were to tighten just by torque value (and no angle spec), using 66 Nm should be possible without plastically deforming the bolt. And a little more should be possible on re-use, due to the work hardening.

The plastic deformation "work hardens" the bolt, meaning that its elastic range has now been extended to include the plastic strain.

So when you apply 56 Nm, and then add 90 degrees, at some point in that 90 degrees, the bolt "should" begin plastic deformation. You might feel this as a fairly sudden change where pulling further on the wrench is not actually getting much more difficult. Once done with the 90 degrees, the bolt (and maybe nut too, since these are not TTY bolts, they are just regular bolts used in a TTY application) will have plastically deformed, imparting a permanent stretch to the bolt (and maybe deforming threads too).

Ideally, when re-using these, you should theoretically be able to tighten it back up to this exact bolt stretch multiple times with no problem at all. And all this would be in the elastic region, with no further plastic deformation. The bolt would be performing exactly as intended.

So that is the goal = tighten it up with the exact same stretch, or "strain" to use the proper term. Not easy to do. And certainly less easy than telling other people to just use new ones.

Following the same 56 Nm + 90* will definitely not do this, since the 90* will be pushing further into the plastic region each time it is done, until finally the ultimate tensile stress is reached and the bolt will snap.

If you knew the torque applied the first time, when you did the 56 Nm + 90*, perhaps 70 Nm, you could apply that pretty safely. Maybe back off a little.

If you feel plastic deformation (when angle increases without a linear increase in torque required), you've gone too far, so stop. So this is what I do, torque to the torque value, but ready to feel for plastic deformation and stop.

If you want to follow the instructions, but modify them, as crystalworks suggested, with 75* rather than 90*, I'll say something like that makes sense, but I don't know if the answer is 75* or 30*. This would be TTA rather than TTY, and should be the most reliable way to do it, if you knew the correct angle.

To answer that experimentally, you could start with a new bolt, install with the spec of 56 Nm + 90*, and measure the actual torque when you reach 90*. (Ideally there would be some time spent here to let things settle out). Then back off to a low torque value, torque to 56 Nm, and measure the angle required to get back to the final torque you just measured. In theory, with no change in surface conditions, that angle should be repeatable. But it's not perfectly repeatable, so at this point, it is easier/safer/more profitable to say replace them.

It would be great if someone some day would do this experiment with a new bolt.

Also, if any of the purists who use these things only once would like to send me their old throw-aways, I'd be happy to test and post any findings.

Is there any way to test a new bolt and then locate a bolt that is the same but is not so expensive that could be recommended whenever this issues pops up?

There is no science or technical data provided by either side of the "debate." BMW does not provide any either, publicly anyway. Anecdotal is the strongest "science" being provided at the moment. blktoptrvl chimed in with input from mechanical/civil engineers as well in regards to the properties of the bolts themselves. Earth was flat point was reductio ad absurdum to say the least. Pythagoras theorizing the earth was spherical is far removed from having any relation to these bolts.

The only other personal experience I can provide is that none of the techs at the shop I was at would replace those bolts, or torque them with the suspension loaded.

The nuts on tie rod ends, ball joints, etc are all recommended to be single use.

What is the thread pitch?

I think I will just go ahead and order 4 (cheap) M10x60s Because I know at least two will have enough clearance. And then order two (Grade 10.9 M10x55 BMW) If I can't find the same from a non OEM source.

I'll put them on the shelf just in case. And next time I drop the place see if the sixties will fit in all locations.

The flat earth reference is not an RAA but it is suggesting what has been attributed to Pythagoras's conclusion the earth is round was a scientific conclusion that was ignored due to so much anecdotal views to the contrary.

It is very simply flawed to make a conclusion from personal experience, especially with this small of a sample. Opinions, anecdotal input have absolutely no connection to science or technical substantiation.

There is no reference in the service manual recommending replacement of suspension hardware. I have seen that recommendation from aftermarket vendors. But as you said it is a recommendation. That is not the same as DO NOT REUSE.

As far as some technical support to not reuse the bolts see posts 65 and 66. I have an open mind to consider any supporting scientific data you can provide. Otherwise, your rationale for using the bolts again is flawed, so it is clear, flat wrong. More of the same will not change that.

Speaking of spheres... this discussion reminds me of one. We've both agreed there is no scientific data to support either position. So...you replace them, I'll not replace them. Others can decide from the experience of others on here what they want to do.

BTW, cheapest I've seen these is at Pelican for $14.75 if anyone wanted to pick up a set. Looks to be "cheap" or these.

I have been exposed to technical data re nuts/bolts, thread pitch, bolt strength, TTY etc. etc. This bolt is not TTY bolt from the look of it.
BMW engineers always overkill when writing technical manual for liability reasons.

The truth is: BMW enthusiasts, being enthusiast, read the repair manula like a Bible.

BMW mechanics: they re-use the bolts all the time.
The only time they use new bolts is engine head gasket job.

We don't agree. I have provided links to technical data and invited you to do so.

$14.75 for the whole set of bolts? Or for each bolt? If that price is for the whole set then I can just get new ones— I always thought they cost way more than that.

"Exposed" is entirely different than educated. "By the look of it" means it is a guess. It's an assumption to state BMW engineers overkill due to liability as rationale to ignore the do not use statement. How many BMW mechanics have told you personally they don't replace the bolts and how many dealer parts dept. have you asked if they stock the bolts? How many techs have told you the only bolts they don't reuse are the cylinder head bolts. "The truth is" statement has no merit either. The readers of an X5 manual accept they do not have the knowledge to tackle a DIY without a qualified source for instruction, specific information etc. I suspect they follow the manual to the letter until they are positive there is a better way or the manual is inaccurate. Posting they are blind followers or it is their repair bible is insulting. Following directions is a strength not a weakness.

For some, not necessarily you, it doesn't matter how important it is to follow instructions to the letter. They will justify their actions, in this case to cut cost, by seeking any kind of support for what they are going to do anyway. Those that have posted here that are not replacing the bolts are doing so without a factual foundation for their decision. When you are posting an opinion it really helps readers to start the post with--IMO-in my opinion--- or something similar.

FYI- I don't follow directions all the time. I feel sure we all know that sometimes it works out fine, sometimes it doesn't and sometimes it is an expensive lesson. Over the last several decades if I don't know for sure there will be no problem if I ignore directions, I have chosen to be safe than potentially sorry.

I think the core issue is the cost that drives seeking justification for taking the risk. Ask yourself--knowing BMW clearly states to replace the bolts and if the cost was $1.00 ea. would you ignore the warning and reuse them? Do you reuse cylinder head bolts?

The dealer list cost is $20 ea. It makes no sense to me and it doesn't to my parts guy at the dealer either but that's the cost.

My cousin is an independent BMW mechanic in L.A. area. I also know 3 BMW mechanics here. They just laugh at the whole thing. They re-use the bolts.

Cost for me is not an issue, I can afford the bolts. I have discussed this in detail in another thread, this bolt is as big as the wheels lugs. It is not TTY bolt.

I don't really care what you say. I reuse the bolts. I think people need to use their own judgment and stop being fearful.

I ways use new cyl head bolts. That is probably the only place I care about using new bolts.

Oh, it is four mechanics, certainly they are representative of all techs. Of course everyone uses their own judgment. Even when they let someone make a decision for them it is their judgment to do so. You are still missing the point by being locked in thinking I am trying to influence anyone's decision. The effort is merely to contribute information to help readers make an informed decision. I have no skin in the game. Unfortunately that challenges your opinion. Well past a lost cause to reach common ground. There is no intention to offend you.

No lost cause.

I find it amazing people spent countless hours discussing a stupid bolt.

Volvo, BMW etc. etc. says change the crush washer on the drain bolt when changing oil. I challenged that theory by re-using the same washer (just pay attention to the orientation as the bolt creates a small indent on the washer, so keep the same orientation). So my Volvos and BMWs have the same crusher washer from factory (I bought some of these cars new from the showroom), after so many oil changes. I keep the brand-new crush washers in a container, I have so many of these washers, it is not funny.

This goes to prove that not everything mentioned in the repair book is that important. I create new procedures for repair all the time.

The only place I care about using new bolts is cylinder head job.

Some Honda factory manual tells people to use new wheel bolts when they replace their tires LOL...

Just curious--when you have the new crush washer why not use it and why keep them if you're never going to need them?

Re crush washer:

1- By using the factory crush washer, I just want to disprove the theory that "one must use new crush washer."
When you think about it, a new crush washer gets "crushed" when being tightened and it forms a new shape...next time look closely at it, you will see the indentation. During the process of removing the drain bolt, there is no damage to the washer. During the next tightening using the same torque, there is no damage to the crush washer. So why replace it?

2- I keep brand-new crush washers just for fun. Just to show people that one does not have to blindly follow the book. One must use his/her own judgment.

Are you referring to that post? I didn't see anything mentioning these bolts and this application. Maybe I missed something?

There have been more than 4 techs posted that do not replace these bolts. We had 3 at our shop. I'm sure there are plenty of dealer techs as well who do not replace. There are more users here who have reused bolts with no issue. The numbers are growing... and as long as the bolts stay $15/ea the numbers will continue to grow. None of that would be enough to sway you.

I've seen this position from you in the discussion regarding the value of different trims vs standard wood trims. Unless someone here posts studies or published figures, nothing we say is going to convince you... which is fine. Neither side is going to persuade the other and replacing those bolts makes you feel you have guaranteed a certain level of safety for the vehicle. That's money well spent if you get that kind of feeling. So again, you replace them, and others won't. :dunno:

BTW, thanks for suggesting the plastidip for the front grilles. The OEMs done in black with glossifier look so much better than those cheesy 6'er style grilles I had on there. I've always been skeptical of dip, but it seems to be holding up. Just weird to have that rubbery feeling. I'm sure I'll get used to it.

I don't understand your question will need to explain if you want a response.

I have considered not challenging advice that is a based on a perception or assumption or a questionable source as it is invariably interpreted as disagreeing with someone just to be contrary, beating it to death or I won't accept I am wrong. But no. I don't care if I am right but do care if if posts are inaccurate or misleading. I only point out the flaws in how they arrived at their conclusion.How How would you answer these questions---Since it is clearly stated in the manual to replace the bolts Dealer and perhaps the tech would be liable if something bad happened because they didn't do so and since the owner pays the bill why would they reuse the bolts? Techs may believe they don't need to be replaced and may be right but what is the reason they reuse them on a customer's car? If you were the owner of the business would you fire them if you found out?

Good day all!!

Can't we all just agree to disagree?! I reuse all mine on all my X5's... They are tight and don't rattle... Never had one break... I use an impact to get them off and back on... I don't remember ever putting a torque wrench on them... Shrug! I have about ten spare sets cause I hit the YPIY's all the time... I always found it odd they used an all-thread bolt... But, whatever!!

Cheers!!

Drawing a blank--what does YPIY mean? I'm very willing to agree to disagree even though I don't disagree with reusing the bolts. My dealer doesn't stock the bolts. I don't think a rattle is documentation the bolts should not be reused. I have never heard of something bad happening from reuse. I have never heard of anyone breaking one when they tightened a reused bolt. I am well aware I am the only one in this thread that has said they buy new bolts. I hate the perception of me that I am contributing to. I feel stupid when the parts guy asks me if know how much they cost. If this is a surprise-- I agree with you---"whatever"

Does the following cause you to question your judgment at all?

A crush washer is a spreading gasket that is not damaged by heat or weather.
The crushing minimizes the risk of damaging the pan threads.
The cost of a new crush washer AND bolt is $.95.

You sound like an armchair general.

I have told you many times that for me cost is not an issue and you still ask! I bought some of these vehicles brand-new many years ago, so again, cost is not an issue.

I want to challenge the conventional wisdom that a washer has to be changed every time. And I have proved it over the last 25 years.

I work in a world of science and we challenge conventional "scientific" wisdom all the time, if we never challenge the old thinking, we will never move science forward.

Good day bcredliner!!

I'm not picking on anyone and I would never tell someone they are wrong for doing what they believe! That takes away from the individual freedom everyone has! That is just not something I would do! I think you have your justified reasons why you would replace them! Absolutely! I agree you should because you think you should! Really, who am I to try to change your mind?

For example, I torque head bolts unlike any others... I do the initial torque, in sequence, three times... I've found inaccurate distribution of clamping force over the dozen bolts as each is added into the load... So, if someone wants to know why, I'll tell them... if they think I'm ready for the insane institute, I agree and move on to the next topic of discussion... LOL!

The "You Pull It Yard"... I had used "PIY" in the past, but I think it was still confusing...

Cheers!

I didn't interpret anything negative in your post.

Listen closer. I offered you information to consider. I asked you a few questions. The only reference to price was indirectly asking why you wasted your 'creative' mind doing something different when for ninety five cents you can do what is proven. I have no idea how that is an example of challenging convention wisdom since there is no wisdom in it. You wasted your time. The is no value perceived or otherwise. Are your seriously selling that as an example of your talent?

Here's my contribution to your credential dick dance since you think it means something. Accelerated MBA from Harvard paid by employer. 15 plus years in product and brand management and 10 years as division President. All in fortune 500 companies. If you are familiar with product and brand management you know the winners have the best expertise designing product and deciphering what is fact, perception, opinion ------. Success is in being out of the box, innovative products that are void of known risks and anticipating new risks that may come from the innovation. I started working on farm equipment at 10. I started modifying my first car at 14. I built and raced Corvettes for a several years. I have never had an adequate budget so there was always shade tree engineering.

There are several reasons techs might reuse the bolts:

1. A customer is not going to like a line item on the invoice for 6 bolts totaling $100ish.
2. Years of experience working on these vehicles have resulted in no negative occurrences of reusing the bolts.
3. Limited availability of the bolts from local sources.
4. No reported failures of these bolts, accidents, etc from reuse of the bolts.

If I were the owner, no, I would not fire them.

I understand your posting now about replacing the bolts (I think). You meant it as a cautionary piece of extra information to consider when deciding to replace them. I think the only reason you've received push back was the tone of the phrasing. No big deal, just took awhile to work through the intent. That happens on forums sometimes.

+1 these stiffening blots have been reused a number of times in many of the X5s and there has been no significant ill versed effects from using them. Personally I think its more of a revenue generator for BMW parts/service by requiring placement of the bolts.

Thats what most repair shops do use a impact on and off and reuse the bolts.

No need for chest thumping as others said. You come across as being arrogant, just read the tone/phrasing in your sentences.
Btw, my resume will put your Harvard thingy to shame, but no need for me to do the chest thumping like you did.

And yes, I have built many engines from scratch.

PS: the guys that wrote the BMW service manual could be an engineer straight from school, i.e., rookie. Thus this thread lol.

Food for thought: if the FSM states that one must replace the wheel lugs at every tire change, would people do that lol?

No food in that thought as it is not a realistic comparison. However, the common sense conclusion is that there is insufficient information to make the best decision.

Tone/phrasing is easily misinterpreted in writing--no body language. My comments are not intended to belittle you or anyone else. They are intended to be focused on the topic. While tone and phrasing can be easily interpreted as arrogant. Comments that I sound like an arm chair general, arrogant and chest pumping are insults. Adding LOL or words that can give you an out of saying you are kidding and don't be so sensitive are BS. In my opinion words like "Btw, my resume will put your Harvard thingy to shame, but no need for me to do the chest thumping like you did" cannot be misinterpreted. They are arrogant, sound like an arm chair general and are King Kong size chest pumping----Oh almost forgot LOL--just kidding.

Being a scientific mind you know how to quantify and prove a theory. And you are very aware that--- that's what everybody does, the manual could be wrong, it looks like and opinions are not enough for a defendable conclusion. You know that directional indicators can be helpful in proving a theory but have some level of risk of being misleading. You also know that to prove a theory it is vital to test the starting point for accuracy.

In this case it seems a decent approach would be to start by finding out if the warning was a misprint or error. If it was intentional and accurate we would want to know the design criteria and test to see if the bolts at to spec. Then test the bolts on an X5 pushed to performance and safety limits. Somewhere there or after other scientific gymnastics we would draw a conclusion. Still doesn't mean conclusion would be correct but it would minimize the risk of error. (Disclaimer-the preceding is a crude broad sweep at a 'scientific process'. It is not intended to complete or orderly.)

But what about common sense? Picture a contest. An X5 will be pushed to its performance and safety design capability limits. We are all contestants. We can request they use new bolts or use the bolts out of our X5s for the test. If the X5 passes a test at max performance and safety the design was based on we win a new BMW of our choice, a billion dollars, a lifetime supply of bananas and a lifetime protection from irritating crap like this. We get to ride in the backseat of the X5 tested and have to give up our X5 if we make the wrong decision. Now the risk and confidence we have in reused bolts is a quantified risk/reward and common sense should prevail and some clarity about what drove our decisions when there was not a clear risk/reward.

Stiffening plate?
 

Are you guys talking about the amluminum skid plate?

I took mine off years ago. I use it for a serving tray on popcorn and movie night.

From my limited background in structural engineering, I think BMW wanted to build a tank that seats 5 and is comfortable. Its overbuilt, heavy and very safe.

I'm sure the plate is an integral part of the subframe.
It's up to the owner to decide if it warrants new hardware.
Personally, I reuse them.

Everybody here has vast amounts of personal experience and trainin Unless it's a Yugo, it's prolly built to withstand
a copious amount of poor maintenance and still be reasonably safe.

even BMW dealers reuse them.
 

I took my X5 to dealership several times for repairing oil leaks, and they removed the plate every time to check out where the leak came from. If they were required to use new bolts every time they removed the plate, those bolts should look very new. However, when I found another fluid leak, I took down the plate myself and would like to check it before bringing in the car again. I saw those bolts were old and the tips of all of them were rusted. Obviously, the dealership did not replace the bolts in previous repairs. So I think using the old bolts is fine and it is not critical of the safety of the vehicle.

This has been debated sooooo many times. The vast majority agree with you and reuse the bolts based on lots of members that have done so and had no problems, dealer input or what their dealer(s) has done.

If you are comfortable reusing the bolts without the knowledge as to why BMW says not to then it certainly is a cost savings. Consider the bolts are stretch to torque bolts which you can only do done once and bear in mind a single experience or the entire tally here may be accurate but the sampling is far too small to accept the results as statistically accurate. And it won't ever be. It is still an assumption either way.

I couldn't care less what anybody does and I get lots of flack when I post this input. If I didn't think it was important to throw in each time this comes up I certainly wouldn't keep doing it.

Again, the vast majority reuse the bolts.

The aluminum plate is a structural member because it acts as a diaphragm, but if you bolted a piece of plywood there it would act as a diaphragm also. I believe that the main purpose of the aluminum plate is to collect fluids that drip from the engine. If you look at the plate it also has an absorbent material lying on top of it. This absorbent material does not contribute to the structural capacity of the aluminum plate, but it does retain a copious amount of fluid. After all, when you pay that kind of money for a BMW you don't want the BMW leaking fluid all over the marble floor in the garage.

Pass me the Grey Poupon!

:rofl:

Wait!! Marble? How gauche... Now granite on the other hand...[emoji38]

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Round and round we go... wait I've seen this tree.

granite? Very passe. I'll have quartz thank you very much. ;)

[emoji38] Now I'm glad I didn't bring up anything about the choice of condiments...

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On hamburgers, pickle relish all the way [emoji12]

Don't ever order a Hot Dog with Ketchup....

[emoji38] no ketchup? Let's not get crazy now...

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What you guys doing here? Have a BBQ party?

Yep No Ketchup!!! According to Dirty Harry.

https://news.wttw.com/2017/08/23/ask...t-dogs-chicago

I have to have ketchup on dogs, burgers etc.

That is totally the Armys fault since they thought tarragon is a great additive to spam, beef and everything that was slapped on a tray....[emoji38]

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I’m totally with that - relish on dogs too! [emoji38]


2005 X5 4.4i (04/05 build date)
Titanium Silver w/Black Interior

Mustard. Nothing but mustard belongs on a hot dog.

FCPEuro's life-time replacement warranty policy made replacing the stiffening plate bolts a no-brainer for me - just replace them if you purchased them from FCPEuro! Why? You get your money back when you send in the old bolts and buy new ones from them, as per their life-time replacement terms. Note - your money back in the form of payment you purchased the new ones, as opposed to a store credit :thumbup:. So essentially the only cost to you for replacing the bolts is the shipping costs for sending the old ones in. Shipping is free when purchasing. Does that now settle this debate for good?:dunno:

Good idea! But no... lol, no it doesn't. ;)

There is no debate really. It's BMW's recommendation to replace vs. the years of experience from owners, indys, and even BMW's own mechanics who reuse the bolts. But then again BMW recommends replacing all suspension fasteners anytime their are touched too... nobody does that either (unless a new part is being put in that came with fasteners). :dunno: Each owner will have to choose to reuse them... or not. With as often as my plate is removed (3 to 5 times a year) I wouldn't even go for the FCP Euro swap out due to the hassle involved. Cost is only one factor.

The only reason that has any substance to it that supports replacing these particular bolts is that they are torqued to a level and THEN torqued to an additional percentage (90 degrees or what ever). That means they are being stretched. None of the other bolts on the car that I've run in to that BMW says should be replaced have this requirement. That tells me the bolts are fine to be reused. I always put blue Loctite on them, but I don't replace them. I haven't had to pull my skid plate yet, but given the torque requirements involve "stretching" already torqued bolts, I'll probably replace them when I have to drop the plate. Just my 2 cents.

The justification for reusing the bolts is always interesting and fun reading. Lots of personal experience, it's a scam, accumulation of what others do or shade tree engineering guessing.

Here are some sources that provide information about Torque to yield bolts such as those used to secure the reinforcement plate. Most of it is about cylinder head bolts. My guess is after digesting this input, even if the cost of the bolts was the same as those used to secure the reinforcement plate, the common sense folks would not reuse the head bolts. The only difference is we know why the bolts should not be reused and what can happen if we do. https://www.youtube.com/watch?v=xFzTZG4eU70 https://www.freeasestudyguides.com/a1_4.html https://video.search.yahoo.com/searc...bf&action=view. I'm not trying to change minds. I am pointing out that until you know for sure why TTY bolts are used to secure the reinforcement plate and what happens if you don't, the risk of reuse is not quantifiable. The risk could be low or could be high, none of us know where it falls. Are you having fun yet?

Agreed. But at some point collective information becomes accepted practice. Some will never change their mind, and that's fine. If it gives someone the warm and fuzzies to reuse these bolts... have at it. If it makes you feel safer or otherwise in a better place, it makes sense.

Head bolts are an apples/oranges analogy though. No one should ever reuse head bolts. There are TONS of documented cases/information of what can happen reusing them. And they are cheaper than the stiffening plate bolts/nuts anyway and not a regularly removed service item. There are no cases of any negative affects of reusing the stiffening plate fasteners except for one user here I believe who reported a squeak or noise from the plate. I am not trying to convince anyone of anything. Just counterpointing your last post.

If these bolts were a dime a dozen, we certainly wouldn't be talking about whether to replace or not. They are expensive and FCPEuro has an answer for us. My strategy in replacing them with new ones is to wait until I've completed the final-final-done-done task requiring dropping the reinforcement plate. Otherwise I just re-use those bolts in the interim.

Possibly, but I don't think it's the only reason. I think, more often than not, they get reused because it's easier to and individuals don't have access to the parts dept or WorldPac. Simple. Couple that with the real possibility of having to drop that plate 5-10 times a year and the motivations are easy to see, including cost of course. :dunno:

Disagree. At what point something deserves to become standard practice is subjective and will vary widely.

A standard practice is not subjective. It is based on a particular set of parameters that prove it is the fact based process.

The number of times the plate is dropped a year should not have anything to do with it. Why would anyone need to drop the plate 5-6 time a year?
This is the best debate of this issue we have had since there seems to be some consensus that high cost drives the decision to reuse the bolts when it clearly should not.

Stiffening plate removal / reinstallation
 

I guess it all comes down to - data, consensus, collective information, sufficiency or insufficiency aside, if you want to replace your bolts, replace them, if you don’t want to replace your bolts, don’t.

Kind of like how many licks does it take to get to the center of a tootsie pop, short of finding the engineers that designed the plate and the bolts and asking them their logic behind it..., the world may never know [emoji12]


Though it has been an enjoyable debate to follow.

That would be an X5 with serious issues. I think 5-10 times a year would be in the category of an exception rather than the norm. I've worked on my X5 since CPO warranty ended (2011 thereabouts) and I've had to drop the reinforcement plate may be 3-4 times in 8 years.

2006 bought new. Haven't had to drop the plate yet. I have a slow leak on the pan gasket. May have to drop the plate to replace that, but nothing else.

Fastenal, Bolt Depot, etc. will sell you very similar Class 10.9 bolts for a fraction of the cost BMW charges. If you feel the need to replace them, at least pay a reasonable price for the bolts.

AM.

Subjective as to when that "particular set of parameter prove it is a fact based process." Not every standard practice is backed up by engineer reports and experimental testing, or is even fact based. IE: BMW used to recommend 15000 mile OCI... nobody who valued their BMW followed that recommendation. Standard practice was 5000-8000 mile intervals among car enthusiasts.

Subjective. It has nothing to do with it for you. It might be the only factor to someone else, or a contributing factor to yet another person.

As to the plate needing to be dropped 5-10 times a year... mine has been off 3 times so far (once for sway bar bushings, once for cleaning/degreasing to track an oil leak, and I don't remember why the third time... maybe for fun?). Will be off again when I do the differential fluid in the coming weeks. Again, we are talking a subjective point of view. 5-10 times sounds like a lot to some of you, but to me, I'm likely to hit at least 5 this year. Dropping that plate is barely past removing wheels/tires to me, which I do a lot for cleaning. Am I strange? Probably. Certainly wouldn't be the first time I'd been called that.

How many times one drops the plate a year is not subjective, it is not a personal opinion. Personal experience is not subjective, it's what we have experienced. I wasn't challenging how many times anyone would need to drop the plate 5 times a year. I was just interested as to why so many times. I thought you were saying most people drop the plate 5 times a year.

Put aside common practice, standard practice or whatever and focus only on the bolts. The bolts are torque to yield bolts. Torque to yield bolts are designed to be used only once, never reused. It doesn't matter where they they are installed.

Very well. We'll change the terminology to common practice.

Put aside common practice, standard practice or whatever and focus only on the bolts. The bolts are torque to yield bolts. Torque to yield bolts are designed to be used only once, never reused. It doesn't matter where they they are installed.[/QUOTE]

:thumbup: on the attempt to clarify terminology. That usually helps. But while we're trying to keep the discussion precise and positive, I'll point out an error in your second sentence here.
"The bolts are torque to yield bolts."

That's not true. They are regular M10 - 1.5 x 55mm, class 10.9, hex head with captive flat washer, and a 10.9 hex nut with flange ... nuts and bolts. Some bolts are specially designed to be used in a torque to yield application, for example with a long unthreaded reduced diameter neck, so all the yield happens there rather than in the threaded section. These are not. They are regular bolts.

BMW specifies that they be torqued using an initial torque plus an angle. TTA. They also specify that they be replaced when removed, which suggests that they are TTY, or torque-to-yield (that following the TTA spec will cause plastic deformation). But it is not 100% certain that they yield when following the TTA specs. To be careful, I assume they do.

So in short, they are regular bolts that may be used in a TTY application.

Carry on. :thumbup:


EDIT - and a similar situation I thought of just now is the breakaway bolts on the auger shafts of my Honda snowblower. They're sold by your Honda snowblower dealer as special bolts, and when I bought the blower I bought a 10-pack for convenience. But as my supply dwindled and I looked into it, they are just M6 hex head, Class 8.8 bolts. Not even annealed or anything. Regular bolts, used in a breakaway application. Which makes sense, of course. Why make something special (like an annealed M10 when you can just use a standard version of a regular bolt). Same idea.

:thumbup: on the attempt to clarify terminology. That usually helps. But while we're trying to keep the discussion precise and positive, I'll point out an error in your second sentence here.
"The bolts are torque to yield bolts."

That's not true. They are regular M10 - 1.5 x 55mm, class 10.9, hex head with captive flat washer, and a 10.9 hex nut with flange ... nuts and bolts. Some bolts are specially designed to be used in a torque to yield application, for example with a long unthreaded reduced diameter neck, so all the yield happens there rather than in the threaded section. These are not. They are regular bolts.
Never heard they are standard bolts before. Where did you find documentation? Great! Anybody have a link to the exact bolt?

BMW specifies that they be torqued using an initial torque plus an angle. TTA. They also specify that they be replaced when removed, which suggests that they are TTY, or torque-to-yield (that following the TTA spec will cause plastic deformation). But it is not 100% certain that they yield when following the TTA specs. To be careful, I assume they do.

Didn't you just write that you assume there is plastic deformation (stretched to point they won't return to original specs)? That means they are not reusable. Standard or otherwise. If there is plastic deformation they should not be used again as the clamping power will be less than spec. We can't be 100% sure but oh well?

So in short, there are regular bolts that may be used in a TTY application.
So BMW states the torquing process of a TTY bolt just for grins, so forums can debate this forever?

Carry on. :thumbup:


EDIT - and a similar situation I thought of just now is the breakaway bolts on the auger shafts of my Honda snowblower. They're sold by your Honda snowblower dealer as special bolts, and when I bought the blower I bought a 10-pack for convenience. But as my supply dwindled and I looked into it, they are just M6 hex head, Class 8.8 bolts. Not even annealed or anything. Regular bolts, used in a breakaway application. Which makes sense, of course. Why make something special (like an annealed M10 when you can just use a standard version of a regular bolt). Same idea.[/QUOTE]

oldskewel is correct,

I have removed the bolt many times and compare it against a brand-new bolt.
There is no deformity of the old bolt from repeated tightening and loosening.
In other words, the old bolt does not lengthen when compared with a brand-new bolt.

The fact that a bolt is angle-tightened does not mean it is a "use-once-and-discard" type of bolt.

This has been a funny thread, especially if read by BMW or indy mechanics, as they do not replace these bolts.

^ Thank you! I was going to order one of these bolts in my next fcp order just measure it. LoL

Thank you to oldskewel as well. I was curious if they were even tty bolts or just used in a tta application. I was going to ask what was making us assume these were tty bolts... The torquing procedure alone? I recently did the complete front suspension on the wife's e70 and a few of those use a tta torque procedure as well. But are not stretch or tty bolts.

The key is the torque process when it includes the statement to no reuse the bolts. But let's assume it is a standard bolt. Why does (not why do you think, not an opinion or guess) BMW state not to reuse the bolts?

It's not about what is the right decision. I certainly acknowledge I don't know the answer. This certainly is not standing on ceremony. It is about what information one uses to make the correct decision. I am challenging responses that are based on false premises and input that cannot be extrapolated to a conclusive decision. There has never been a trained bolt expert that is behind the decision to reuse the bolts. It always boils down to---most people do, BWW and Indie techs reuse them so it's OK. I think the decision to reuse the bolts would be the same without any input one way or the other---it is entirely cost driven.

I agree with what was said earlier---until we have an explanation directly from BMW the debate will continue--we still don't know why the statement or what happens if we ignore the instruction. IMO that information is the only information that is or can get to a conclusive answer. Please hurry, I have my X5 up on stands to change diff ratios so plate will be coming off.

It was fun for awhile. I enjoyed some of the comments. Ya'll be happy to hear I now think this is frustrating, irritating, meaningless, a waste of time, beating a dead horse and a bunch of other stuff like that. I'm glad to have provided at least some of you some laughs.

Here are a couple of links to the actual BMW bolt:
https://parts.bmwofsouthatlanta.com/...lt-31101096987
https://www.ecstuning.com/b-genuine-...r/31101096987/
If you google on the part number, you'll find the exact same bolt used in many applications other than for the reinforcement plate on the X5. That, along with everything else about it, suggests that it is a regular bolt. (well, a regular Class 10.9 ...)

The spec is TTA. Whether it actually yields or not is not certain, as far as I know. I've seen signs of deformation on some of my own bolts, but maybe that was from someone overtorquing at some point. I expect that the TTA takes it close to yield, if not into yield. So to be conservative, BMW specifies replacement, and I act as if yield occurs, whether or not it does. Yes, the fact that BMW specifies replacement, I take to mean that they think it might be yielding.

And no, yield (plastic deformation) of a bolt, in general, does not definitively mean it is not reusable. Not at all. Plastic deformation in a steel bolt will cause work hardening that strengthens it, so it should be able to return to the same amount of stretch with no further plastic deformation (all elastic now).

It's not a TTY bolt, as I tried to say. It's a regular bolt, used in an application with a TTA tightening spec, that may or may not result in yield (if yes, then TTA becomes TTY), probably causing BMW to conservatively suggest replacement, which almost everyone ignores with no ill effects.

BTW, TTA is a very accurate way to torque fasteners, regardless of yield or not. So if yield is known not to occur, a TTA spec will result in more predictable clamping force than just a torque spec.

As I mentioned in probably another thread on this general topic (search on this site, there are probably only a hundred or so to look through), the important thing to avoid is doing the TTA repeatedly. If yield is occuring, you can't keep doing the same angle, since each time, you will pushing further into the yield region, eventually causing fracture.

You asked a question, in a specific manner, knowing nobody could answer it.

I'll put it to you an equally impossible task. The E53 X5 has been on the road now for 18+ years. Each and every single one of them has this reinforcement plate on it, with these bolts. Then, cross-reference that part number with RealOEM. It is used on the reinforcement plates of every E46, E53, E65, E66, and E67 equipped with an aggregate protection plate. I don't know what the total numbers of bolts in use on all of those vehicles comes to, but it has to be a huge number. I was unable to find one documented case of failure for the bolts. We are actually the only forum that even discusses the bolts from what I can tell.

BTW: For anyone looking. Here is where you can get them for $12/each. https://www.ebay.com/p/2-X-BMW-Genui...E46/1322230484

Edit: ^ NM on the $12/ea price. It appears the "2X" for $24 is no longer available.

This was my first post when this thread was revived:

"This has been debated sooooo many times. The vast majority agree with you and reuse the bolts based on lots of members that have done so and had no problems, dealer input or what their dealer(s) has done.

If you are comfortable reusing the bolts without the knowledge as to why BMW says not to then it certainly is a cost savings. Consider the bolts are stretch to torque bolts which you can only do done once and bear in mind a single experience or the entire tally here may be accurate but the sampling is far too small to accept the results as statistically accurate. And it won't ever be. It is still an assumption either way.
I couldn't care less what anybody does and I get lots of flack when I post this input. If I didn't think it was important to throw in each time this comes up I certainly wouldn't keep doing it.

Again, the vast majority reuse the bolts."



I felt it gave credence to those that reuse the bolts and did not take a position one way or the other. Since then I have only responded to posts claiming it is fine to use the bolts that I think are based on assumptions and I don't view responses as eliminating those assumptions. I see that I made an assumption the bolts are TTY bolts. I am not convinced they aren't but I now question if they are. This has never been about which decision is right or wrong. It has been about what information has been used to make a decision.

The new information regarding the broad use of the bolts is great. If the torque specs for other uses is exactly the same and there is no statement to not reuse the bolts that is very significant.

I see this as a debate rather than a discussion Generalizing, the purpose of a debate is to present facts to eliminate flawed interpretations of information. It requires two points of view. No individual should be chastised because of their view or input. Even vailed insults are uncalled for. There should be no conclusion drawn as to whether you like a participant or not based on their input. A debate doesn't have anything to do with the kind of person one is. Nothing should be interpreted as a personal attack. It is purely an expression of a point of view. If a true debate one should be able to defend the opposite position with equal conviction. The nice thing about a forum debate is if it generates negative emotions you can opt out of the thread.

In my 1998 528i, FRONT wheel bearings bolts...BMW manual says replace them.

All BMW mechanics I know re-use them. I re-use them, they are as big as the wheel lugs.
That was 10 years ago, the bolts still hold the bearings just fine.

So what does everyone think about using duct tape? [emoji38]

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Duct tape will seal it, but you really need zip ties for the holding power.

I prefer JB Weld Kwik. Best thing out there. Built entire cars out of the stuff.

I don't see any doubt about them being special TTY bolts. But I think there may be some doubt about whether they yield when the TTA spec is applied properly. While responding to another thread right now on oldmactech's head bolts, I was reminded of this thing I noticed when examining my old vs. new head bolts last summer.

https://xoutpost.com/bmw-sav-forums/...formation.html

Should be an easy test for someone who actually buys new ones to compare vs. the removed ones. And if you line up old vs. new and the threads match all the way, you can pretty safely conclude that they did not yield, and reuse them with even more confidence.

Also, regarding applying the TTA, that's only part of it, since the factory, the owner, the PO, the dealer, etc. might not do it accurately. And then once applied, stresses from driving could cause some yield. So different people might find different results, even among their 6 bolts.

I've had my plate off a few times; first was for front differential oil change, last was for top-end engine rebuild. I paid attention the first or second time, noticing some deformation based on the fact that the nuts would not all spin on easily with nut and bolt in hand. So as I've said, I re-use with the conservative assumption that yield has occurred, and not wanting to yield it more, I torque accordingly to a higher but conservative value, without doing the final angle.

from BMW:

(they didn't include the protection from the garage floor, but maybe that is attributed to the foam padding above the panel).

I put my 'restriction plate' (restricts you from getting to anything) back on with some SAE bolts i had handy and am soon going to be removing the plate and putting it back on.

Since it's the way i'm built, i plan to do a ditch-witch maneuver with the plate off with some steel strap snug by not overly tight to measure how much the subframe will twist when i lift one wheel up in the air, probably drive onto a stack of cement blocks to lift it 8".

It's pretty clear that the primary job of the plate is in-fact to keep the front suspension true and not twist; 4 or 5 mm thickness of aluminum times 200mm width (my estimate) means 800-1000mm cross section that's the equivalent of a solid rod of 16-18mm diameter and would substantially hold quite a bit of force. (40-50,000# before yield with mid-grade aluminum alloy; could be double with high strength aluminum)

Since i used under performing bolts and they've been on there a while, if they didn't do their job and allowed motion, it will be very obvious. If they on the other hand, held the plate from moving in spite of being much lower clamping force than the design, it will be solid proof that bmw over-engineered the part and give people piece of mind that they can definitely use normal bolts.

The bolt i found online just now clearly is stamped 10.9. There is no reason you couldn't use a similar bolt from a hardware store except it won't be galvanized. Steel-to-aluminum will set up an ugly galvanic reaction when it gets a little salt spray on it.

The TIS for replacing the plate is here

The torque spec is here

My reference for bolt torque shows 67 N·m and the tech spec above shows to use 56 N·m + 90°. I will also see how a re-used bolt vs a new 10.9 bolt behaves when it's torqued. I have a strong suspicion that the extra 90° will go past the 67 N·m advised torque and puts you from TTA into TTY.

0.0888 in² cross section and yield of 136k psi, means yield force of 12,100# roughly and torqued normally (67 N·m / 49 ft·lb), is 'only' 7531 # of force. Another measurement I will take is what is the actual torque applied to achieve the 90° TTA.

The whole point of this endeavor is to determine if the bolts are even close to their yield strength and there is any need for this debate to continue. If the bolts aren't close to even the proof load of 113kpsi, the debate can be concluded. No damage to the bolt and no reason to not reuse them.

If, on the other hand the bolts are being stretched to yield, then my recommendation would be to slightly under-torque to keep them from stretching or oversize the bolts one size bigger so you can get the same clamp force without damaging the bolt.

A little quick math achieves this factoid: it takes about 89 N·m to get a 10mm 10.9 bolt to proof load, which won't hurt the bolt at all, and about 107 N·m to get that bolt to deform. So, if the 90° after 56 N·m is in the range of about 100 N·m the bolt won't deform and you can reuse it as many times as you'd like; until you hit the limit of elasticity steel acts like a spring and you can basically use it countless times (think of coil spring on a car how many millions of compressions; yes they can fail, but wow it's not likely).

So here is another interesting factoid: switch to fine pitch thread and you can bump the clamping force from 7500 to 8400# per bolt. That would likely be easier than drilling out a hole to 11mm (and finding 10.9 M11 bolts!).

So my summary is that if it can be determined that 56 N·m + 90° ends up at less than 100 N·m of force you did not deform the bolt and it can be reused without any concern.

I am almost certain that the design of the system is that it uses the bolts beyond the advised torque and clamp force on purpose to achieve two significant results: 1; that it will keep the plate from slipping sideways so it can do its job and 2; that it won't wiggle loose; the added forces are simply acting like a lock washer. Similar to the concept of head bolts; using a pre-tension and angle gives you a very precise force based on the elasticity of the steel and simple math (how much longer did you stretch the bolt).

I scoured the 'net to see if anybody ever did any actual tests or experiments on this stiffening / reinforcement plate and found hundreds of posts posing the question and not a single example of finding an answer. It won't be that difficult to figure out a definitive answer, which will certainly give 'seat of pants' guessers some satisfaction that they guessed correctly.

I'm planning to remove my underbelly plate and wife's as well in the next couple weeks to do some hard-core engine cleaning and finding some wayward leaks, so i will do a couple tests when i do so to determine the answer people have been pondering for years yet nobody took the HOUR it will take to answer them.

:popcorn:

AM.

Why does BMW state not to reuse the bolts and what can happen if they are reused?

You should have doubt if the bolts are TTY bolts. There have several posts saying they aren't . However, I think so far nobody knows for sure.

85 or so percent of torque is friction. The other 15 percent is clamping power. If there is deformation there is no torquing procedure that will get to the original clamping power.

Why does BMW state not to reuse the bolts and what can happen if you do?

Based on assumptions, roughly, about , almost certain and estimates. Further, if you don't know the answer to the questions of why does BMW states to no reuse the bolts and what happens if you do it's a waste of time. As an example---are the bolts supposed to stretch? If so, how far, to plastic deformation? What clamping power are they trying to achieve? Finally, if you aren't using industry accepted methods and equipment for testing there is no way to be sure your results are accurate. As I have said many times, I'm not trying to convince anyone of anything. I am challenging the methodology thus far presented to conclude it is fine to reuse the bolts.

You can ask BMW.

Personally, I think BMW has its strength and weakness.

- Strength is in esthetic "curb appeal", driveability, the "name BMW" etc.

- Weakness is: reliability and repair procedure is overly cumbersome.
Technical manuals were written with liability in mind. This bolt discussion is somewhat dumb simply b/c the crazy (paranoid) engineers wrote that sentence of "replacing the bolts" and not-too-smart people follow it like the Bible. Remember "it takes 2 to tango" and I am not part of this tango.

Stiffening plate removal / reinstallation
 

Because they set themselves up for liability. By err on the side of caution they can't be responsible for anybody using anything outside their specs.

The simple math shows that the corners are held with about 20,000# force in the back and 10,000# in the front. It wouldn't surprise to discover that is just enough or to find out it's 4x as much as needed.

BMW guys must see the threads asking and choose not to answer with authority on the matter. It feels like only the guy that designed it knows why and chose not to divulge why so now the only reason anybody does it is "because somebody said so". Since childhood that is not an acceptable answer for thinking people so it drives thinking people crazy when the reason is not given.

I've seen nothing of authority on the subject. (only the generic torque spec sheet with what but not why).

I have driven the X5 without the plate and can absolutely feel the difference in the front end so It definitely does it's job. I can also say that with much smaller bolts it firmed right up so for the majority of the function it does not need nearly the spec clamping force. (I will measure the current torque/clamp force on my plate now to get a sense of what might actually be required).

I will not be too surprised to see that my plate has signs of sideways slip but it won't surprise me if there isn't either. There is a good amount of surface area clamped together so there is likely some force multiplication e.g. with 7500# clamp force it might take 12000# to move it sideways.

When you hit a big bump on one wheel it could easily generate forces on that scale and I'm sure that went into the why In the original design.

Unless someone beats me to it I will be getting some very useful data that can be used to decide which route to take.

The "easy way out" is to assume BMW is infallible and follow them blindly. That solution will have you paying $920 for replacing the four door lock motors (parts only) vs $24 for the actual motors.

If there was even one single paragraph with authority explaining the why, it could end the debate.

There are people that recommend leaving the plate off. Terrible idea, the other extreme is to always replace the bolts. The most logical solution I guarantee is in the middle. And I diagree that it's all about cost: if the bolts were an appropriate $2 each I would still want to replace only if it's logical to do so: we don't replace our bolts each use but nobody worth their weight in cheese will reuse a head bolt that is just moronic.

I contend that it's not much smarter to replace a bolt "just Because" if it works out that the bolt has no wear from normal use. It's much smarter to get some informed data and proceed on a logical path.

If the 56+90° ends up taking 120 N·m and is well into plastic deformation I would not reuse that bolt. I would probably get a new bolt and pay attention while installing and stay in the non deformation zone as long as I can back it up with some math.

Eg if the spec is 7500# clamp force but you can achieve 7000# without distortion you can believe that is what I would do (or switch to fine pitch bolt etc).

This story will continue. Withing a couple weeks I will be doing some measurements that will give us some actual values not striaght up guess work.

I will take a new bolt and TTA while measuring the torque applied to get a decent estimate of clamp force. From that I can reverse engineer what straight torque can get a similar clamp force without going into plastic deformation.

If not possible with the stock bolts I will be swapping out the bolts to a size that will achieve the factory design of clamp force without damaging the bolt.

One other thing to consider: the back corners have a PAIR of bolts to hold the sway bar. I would be comfortable with reengineering to have the back bolts backed down to normal torque since that will net 15,000# clamp force and double the surface area on the plate.

This may have just gotten stupid simple. Class 12.9 bolts have a higher yield strength than the tensile strength of the 10.9 bolts. You can buy FIFTY of them for less than the SIX if you buy an official BMW bolt.

I'll be doing some measurements and if simply upgrading to class 12.9 will achieve the same clamp force without going to a bigger size you can bet a dozen donuts that I will have a dozen of them in short order.

The only conceivable risk is they could be brittle enough to break vs stretch more but two things about that : whatever maneuver could cause that, a corner of my restriction plate coming loose will be the least of my worries and it will be nowhere near the clamping force maximum I'm betting.

There are also grade 14.9 which are far above and not expensive "each" but the smallest order I found in a quick search is for 1000 quantity.

So: I'm quickly leaning toward get a beefier bolt so I cab achieve the same clamp force of the design spec but not cause any wear on the bolt. With any luck I'll discover that the TTA causes no plastic deformation and I'll be able to report a torque value that approximates the TTA without hitting deformation. I myself would have no problem torquing to 80 N·m vs 90 N·m if the former caused no damage and the latter meant single use on $60 of bolts.

To be continued.

Using basic tools (peak reading torque adapter) and micrometer it will not be difficult at all to determine several things:

Are the bolts stressed to plastic deformation mostly is the key. If they are not simple formulae exisit to determine the clamping force.

Taking a new bolt and tighten TTA per spec and measure the torque to get there. Remove the bolt and meausue it's length before and after to determine if it's been stretched. If not plug the torque value into the torque to force calculation and you'll get the clamping force within 10-20%.

You don't need anything particularly NASA grade to figure this one out it's not mission critical like a head bolt.

It's my contention that it's an over enginereed part and I plan to test that in a real world way and report the findings. If I'm wrong I'm completely fine with that I'll just use a bigger bolt to achieve the factory design without self-destructive bolts.

It's the blind faith following with no explanation that bothers me and surely tons and tons of others (based on the thousands of posts easily found on the internet on the topic).

If we knew for example that the plate moved a mm every pothole if you attempted to reuse the bolts that's information we can use to side with BMW. If we knew that you could use a 3/8" unhardened bolt for a year and have no sign of sideways slip, that's hard evidence to support single use on the bolts is a crock of crap.

The reality is somewhere in the middle I'm betting.

Completely false. Keep it simple here. Figure that one out before going any further. That is a very basic concept that is part of the first-day lecture on the stress-strain diagram. Really, it is. If I had to give a 5 minute lecture on stress-strain, I'd include that.

You can loosen the bolt and then tighten it to the exact same strain (torque angle, bolt stretch, however you want to measure it) and it will have the exact same clamping force. Theoretically of course. Nothing is really exact. But practically true as well.

Same reason why BMW tells owners that the ATF is lifetime, but if you go on ZF's website they state that ATF should be changed every 40,000 miles, not unless it is revised by the car manufacturer. So who are you to believe, the company that sells the trans to the manufacturer or the manufacturer that buys the trans and install it in the car.

Stiffening plate removal / reinstallation
 

Also somewhere in the middle. If the bolt is plastic deformed from the initial install, it will have a smaller cross section and the next time it's installed using the same procedure it will logically have a lower clamp force that's the entire explanation for single use.

That said it might be higher than proof load but be less than yield so there is no deformation but it's stressed past proof load so NASA can't reuse the bolt, but DIY on BMW yes sure.

Back to the original thought: people are ONLY GUESSING because nobody took the time to take a friggin bolt or two and measure what happens.

It will be laughable if the TTA ends up being less than the normal spec of how much torque to apply to a 10mm bolt.

The debate isn't pointless it preps the mind and mindset for doing some appropriate texts/experiments that can finally answer the question.

If for example TTA process ends up at 65 N·m than BMW are aholes to tell people to replace a bolt that wasn't even pushed to proof.

If the bolt ends up BENT due to sideways loading, that could be another good reason to switch out the bolt.

One way or another I will using a reusable solution in the future. The results of my tests will be shared so finally people can have measured values to use as well to make an educated determination rather than take one of the extreme sides must replace "because it says" or it can't really need it (with absolutely NOTHING to back that up).

My 3/8 bolt (5500# clamp force) for months holding my plate on will be solid proof one way or the other. If there is no side slip evidence on my plate it's absolutely proof positive the M10 torqued past proof is waaaaay more than needed

If the plate has a oval hole worn in because I'm a moron that will be solid evidence that it needs closer to design spec. I'm kinda hoping that there will be clear evidence of motion of the plate. I drive over curbs a lot. If I didn't ditch witch my car into slipping the plate nobody else will.

I've been wanting to follow through with this test ever since I put the temporary 3/8 bolts in. (I didn't want to put the original bolts through more stress since I took them in and out a few times in a week (removed plate to clean engine, put back bolts in to hold sway bar, removed those to reinstall plate, removed again to take plate out to install new oil absorber aka sound insulation then install once more).

I was being lazy the last time when I should have found the original bolts but just reused the ones I had under the car with me.

One last point: BMW is very subtle about the reuse factor it's almost just a footnote it's not like the verbiage of driving without the plate.

Paraphrasing: "under no condition drive the car without the stiffening plate*"

*And if it's not too much trouble you should really consider using new bolts.

The first time through the repair manual I actually read "replace the bolts" meaning re place the bolts you just removed back into the plate. It took a half a dozen re-reads of the TIS before I was confident they do actually recommend using new bolts.

I've got some Pop Secret movie butter ready to go.

Redliner, if you are unsatisfied by anything but a lab certified stress test on these bolts... I don't think you are contributing to the discussion (unless you are going to commission said testing or post BMW's). You've said your piece on this matter stating it's probably safer to buy new bolts because BMW recommends you do. I searched high and low on the many chassis these are used on, worked at a shop with BMW trained techs, am familiar with the mechanics at the local dealership and came to the conclusion that they can be re-used. Have had my plate off a half-dozen times in the almost 4 years of ownership so far. You read one statement in a repair manual and took it as gospel. Which is fine, as I said if it gives you the warm and fuzzies, more power to you. But don't disparage others when there is no evidence reusing these things causes any issues at all. You are putting the burden of proof on everyone else. :dunno:

Like you, we are all ears. Show us how reusing these is a bad idea. Personally, I think andrew is one of the most talented mechanics I've run across and would trust any conclusion he draws from his testing. And am grateful to have him take the time/energy to do said testing.

As mentioned, any BMW mechs or indy mechs who read this... most likely, are laughing hysterically.

I see my work here is done...:popcorn:[emoji38]

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There are many bolts that the manual says BMW says you should replace. Suspension component nuts and bolts are just one. I've reused them with no ill effects. I recently had my seats out and put them back in. The manual calls for them to be tightened to a specific torque plus 90 degrees. The "bolts that the nuts are going on are welded to the body. That tells me that TTA is not the same as TTY. If TTA is the same as TTY, then the seat bolts would need to be replaced. But they don't. Personally, I think BMW's recommendation to replace all the different bolts and nuts they do is a money maker for them.

Insulting others reflects on ones own character.

It is not what anyone's opinion is, the question that needs to be answered is why does BMW states not to use the bolts and what happens if you do. You think it is paranoid engineers and nothing happens. But that is an assumption without any basis in fact so you really don't know. It's just that simple.

Most likely is another assumption, laughing hysterically is an attempted insult. I am not saying the bolts can't be reused. I think there is lots of indications they can. I am saying nothing presented so far is adequate to prove they can.

As I posted recently TTA is a torquing process. The bolt may or may not be a TTY bolt when the TTA process is used. When the instructions also state not to reuse the bolts it is a strong indication the bolt is a TTY bolt. Deciding one way or the other is still a guess unless you know for sure the bolt is or is not a TTY bolt.

Yes, BMW states not to reuse other bolts but we are not debating other bolts. If everyone is reusing the bolts the pricing does nothing. No sales, no profit. In my experience parts are extremely profitable. I would guess these bolts are no exception. But if a standard bolt works fine they are pricing themselves out of the market and it is offensive to potential buyers.

Note that I said deformation, shortened from plastic deformation. Yes, if the bolt does not reach plastic deformation it can be reused. We don't know if the plate bolts reach plastic deformation or not.
https://www.fastenal.com/en/77/reuse-of-fasteners

" But if a standard bolt works fine they are pricing themselves out of the market and it is offensive to potential buyers."

BMW does this with all of their parts. "Genuine BMW" is usual three time what the same part is from the original supplier without the BMW marking.

See paragraph one. https://www.fastenal.com/en/77/reuse-of-fasteners

This caution is more for people that remove the stiffener plate but don't reinsert the bolts to secure the sway bar bushing back onto the subframe. People are stupid and don't realize that when they remove the bolts for the stiffener plate they are also detaching the sway bar from the subframe.

It would be a lot more dangerous driving around with the sway bar detach than it is with the stiffener plate removed.

In the sentence prior I said parts are an extremely profitable category. My guess is some are more than 3 times and some are less, probably based on whether or not there is an aftermarket competitor and/or the sales volume. I suspect BMW has done an analysis of profit dollars of parts sold over the counter and parts invoiced as part of repair in their shop and found that they would lose profit if they reduced the over the counter prices. And, parts stock takes a considerable amount of space. With cost of land and brick and mortar parts have to justify the allocations. As an example, if parts stock uses 20 percent of the space it is likely they are charged 20 percent of the total overhead plus the cost of all associated employes. Over the years my dealer stocks less and less parts. Most of the time the parts are overnighted from a distribution warehouse somewhere. Another reason for the high cost of parts is that the seller needs to make room for discounts for qualified businesses and still make a profit. Some dealers will give a discount to members of BMW car club of America which helps. Might check. Membership is $48 a year. Helps when you can't wait for parts to be shipped or the cost doesn't meet the ship free minimum.

Well done Bcredliner, that article should surely kill this thread. And to add flowers to the grave, here's one thing. Cost to me for 6 new BMW bolts $4 (which is the return shipping for the old, rusty 6 bolts).

You are correct. In my Bentley 2002 X5 service manual there is one box that reads:
"Caution
Do not drive vehicle with reinforcement plate removed. Reinforcement fasteners also serve as stabilizer bar fasteners"

As you well know the second box is what applies to the discussion.

It starts with

WARNING

Below that is the box. It reads:

WARNING---
Do not reuse self locking fasteners. They are designed to be only used once and may fail if reused. Replace with new"

I really appreciate your post. Thank you.

They will not get very far before they realize their mistake (about two car lengths). I am quite sure the "remove the plate guys" put the bolts back in to hold the sway bar..

It's an interesting thought that the plate warning might be related to the sway bar but the identical warning applies to other BMWs that have the type of plate (I think I saw on M2 or M3 when searching for some authoritative verbiage on the stiffen plate)

So "the plot thickens": somebody mentioned they were sure the bolt stretched because they couldn't thread the nut by hand.

The nut is crushed into an oval to make it a type of locking nut. That will certainly throw off the torque calculation and makes perfect sense why use a TTA.

The bolt looks perfect but I have yet to measure the threads for distortion

Consider this: if the crushed nut takes 10 N·m to overcome, the 56 N·m pretension is really 46 N·m. I'm feeling more confident the bolt is not pushed past proof much less yield.

The article was a very good read and the key ingredient was the large increase in torque to achieve the same clamping force; a situation largely mitigated by using TTA.

I don't have any gear that can register 9000# measurement but I have a very precise scale that can do 330# or something so possibly with some leverage I might be able to measure the actual clamp force on a new vs recycled bolt and possibly more important: nut.

So this is the best reading I've found on the topic of TTA : in this particular example where they used 180° TTA they broke the bolt on the 9th reuse and determined that accounting for safety margin that it was perfectly acceptable to reuse the bolt using TTA method five times.

THIS is what doesn't exist for answering the question of reuse of these particular bolts. I'm going to attempt to get a measurement of what actual clamp forced is generated from the 90° TTA in these bolts to determine what loss of clamp force happens with reuse and if there is a cycle count that makes them actually wear out like in the example

http://www.boltscience.com/pages/a-c...tightening.pdf

When I replaced the OFH gasket, I left the plate off for about 3 weeks just to monitor for any oil leak. During that time, I re-installed only the bolts holding the sway bar, the X5 drove the same w/o the plate.

The Fastenal article above does not kill anything. It is just another article on the nuts and bolts.

Do this: remove only one bolt (the bolt in the front area near the front radiator). Then remove one wheel bolt. Now compare them. They are similar in size and strength. And we don't replace the wheel bolts, which are subjected to much harsher condition (shearing force, hitting pot holes etc.).

Wheel bolt is M12 good for 11470# under normal torque and an M10 is good for 7500#. If the TTA is deforming the M10 it won't press as hard each successive re-use. (Well except possibly the second time where it can be higher due to self hardening).

It's all speculation until somebody measures. They don't say why to use fresh bolts they just do. I'm betting TTA and TTY are confused and the bolts aren't deformed now that I realized the nuts are loving nuts that reduce the actual torque. I can't wait to do some tests it's very interesting to me.

If you want to do the test, I would guess you will need to plan to test 20 new bolts and nuts and stop at 10 if the variance is minimal. That's purely a guess.

Depends how close to tolerance. If for example testing five gives you no result closer than 80% of proof stress I would be satisfied that it's all safety factor fortunately I found some 5 packs of galvanized M10 for a very good price.


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Comparing a lug bolt and plate bolt doesn't mean anything. Similar and look the same does not mean they are even close to being the same. They can look exactly the same and have entirely different specs.

If the data from experts is not accepted why should anyone accept your DIY anecdotal input as such? If a conclusion is as based on assumptions , not matter how many times it is posted or variations of same are introduced the conclusive is still flawed.

I don't need anyone to accept my DIY.
My conclusion is based on real life experience.

Your Fastenal article above serves little purpose.
We already know all that stuff.

Now, do a google search using key words "bmw stiffening plate bolt reuse", you will see that 99% of the posts are from DIYers at home and not mechanics. Naturally, these DIYers are concerned b/c they read Bentley manual etc.

Just got off the phone with my cousin, who owns a BMW indy shop in Los Angeles area. All he does all day is BMWs and nothing else. And he has repaired BMW for 30 years. He just laughed at this thread b/c he re-uses the bolts all the time and does not recall one incidence of any problem. He said these are not TTY bolts. rather, they are TTA bolts.
BTW, the only time he ever replaces the bolts routinely is the head gasket job and that is about it fixing BMWs all day long...

So, there you go, you can sit here and argue all you want...

Does he reuse the aluminum bolts that are prevalent on the N-series engines? I HAVE reused them in a pinch, but replace them if at all possible.

AM.

Again, that's fine. It is your personal choice to reuse the bolts based one a statement from BMW, Bentley, etc. Have at it. Literally, nothing posted would satisfy your doubt. Again, fine. But don't discount people who have years of experience dealing with these bolts on tens (or possibly hundreds in the case of dealership or indy mechanics) of vehicles. You have made your decision, and I (don't know about everyone else) respect it.

But when people come here asking if they can reuse the bolts, it's because they have already read the statement you are referring to. They are looking for real world experience from those who have NOT replaced their bolts. Your input is something they already know. If you had proof of some negative result of reusing them, that would be valid input. I include in every response (I think) to someone asking if the bolts can be reused that one member reported possible noises from his stiffening plate and/or the bolts.

As to the comment regarding mechanics reading this thread and laughing being a personal insult. If you are offended by that, or took it as a personal slight, you have thin skin. Mechanics reuse these bolts all day long. They'd laugh.

:bustingup Sarcasm? :confused:

And congrats on finding a way to get the bolts cheap. :thumbup: Seriously. For those who the main factor is the cost that should help considerably.

I read the whole article. Very good read. I was saying the same thing regarding if it's ok to reuse a bolt. All my "it is ok" math is based on don't exceed proof load.

I did my first exam of an old bolt today but since I don't have the "before" nothing conclusive yet, but preliminary measurements suggest the bolts are actually strained past proof, and would have a cycle lifespan like the above article explains. (Eg ok to use 5 times).

I've only measured the bolt after use and I measured a slightly lower than expected thread pitch.

https://uploads.tapatalk-cdn.com/201...899628ee6a.jpg
Over the first 9mm the threads seem to line up on a 2/3 thread per mm or 1.5mm/thread as expected.

https://uploads.tapatalk-cdn.com/201...431b60c12e.jpg

But at 36mm (24 threads), it's clearly about 36.2 mm or 1/2% elongated.

That does strongly suggest the TTA torque is also TTY.

I'm getting excited to get some measurements made

Could you do the same measurement for a wheel bolt?
We re-use wheel bolts all the time and wonder what the wheel bolts look like after 15 years of service...

Or even shorter time periods after tire shops nail them with air tools....

Interesting. Thanks for the pics. I'll have to measure mine as well next time they are off. Get a second point of reference. But to throw a wrench into measuring the old bolts... we don't know their history of torquing. Most mechanics just hit these with an impact, give it a few good uggaduggas, and call it a day. :dunno:

I'm not arguing. I don't know what the correct answer is. I'm just asking you to provide expert proof to support what you have heard and your experience.

There are multiple pages that you posted the bolts can be reused with no qualification of the number of times and prior to posting disagreed with the Fastenal information. Since the bolt is elongated that means the same amount of torque will not result in the specified clamping power. In the testing world instruments can be used to measure the angle increase necessary to reach the specified clamping power. In the real world there is no way to know what amount of elongation equates to what amount of angle increase.

No, it doesn't, unless that is the industry testing method and specs. If that is proof to you that is one thing. If that is used as intended proof that there is no problem with reusing the bolts it doesn't.

Are you saying the nuts not the bolts are the potential problem?

Unless they are over torqued they will last forever. It isn't that hard to over torque though.

Case in point:

https://uploads.tapatalk-cdn.com/201...d40c9d2f4d.jpg

I goofed above when I said the lug bolts were M12 they are M14.

M14 spec is 187 N·m and BMW calls for 130 so 40% safety margin on not damaging the bolt.

The bolt above I believe was tightened with 350 ft·lb impact

I use torque sticks just like the shops. When I spot check with digital torque wrench they are within 6-8% I don't race I'm good with that.


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That was the suggestion. Re using a crushed type locking nut I highly suspect will vary the pre tension torque especially if it's coated in oil!

https://uploads.tapatalk-cdn.com/201...5b3423ece5.jpg

Maybe that's why BMW puts the nut on the top!

I don't know how critical the pretension is in this case but I'm pretty confident that even with 90° TTA the bolts are purposefully stretched to deformation just like the example I found.

In that case they determined five uses is fine they don't lose significant clamp force until after five uses.

I'm going to repeat their experiment on some clones of the plate bolt and see if they will fail after xx uses

The point in all this is to have some definitive answer based on facts.


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Agreed. When I have to drop my plate, I'll buy the cheaper bolts that are the same. Living in CA, I don't care if they're zinc plated. CA doesn't use salt on our roads.

We may be using a different definition of proof. I'm saying that if in my testing I never get within 80% of the design ksi of the bolt I can definitively claim the bolt can be used quite repeatedly.

The odds get ∞ small that I'd pick five random bolts that would all be more than 20% off the median.

I did a little more research last night and came to the conclusion that they are in fact TTY based on the fact that bolts I removed are longer by 0.5%.

I've also come to the conclusion the designers chose to use TTY to achieve a consistent clamping force because it is important to keep the plate tight to do its job of torsional rigidity.

So the cost effective logical choice is to get new clone bolts (M10-1.5x55) and a washer for the aluminum side (you won't find a captive washer bolt). I would also replace the nut with a locking nut of some kind.

The other logical possibly and the route I will probably take for the mere convenience is to upgrade the bolts to 12.9 bolts because by some amazing coincidence the proof load on 12.9 is almost exactly the same as the yield strength of a 10.9 bolt.

The problem with that is that reuse of a bolt it's difficult to achieve the same clamping force (shown in the study above for for example the torque required climbed by about 10% each time)

I'm confident that issue can be resolved by lubricating the bolt which is good since my bolts are "self lubricating" at the moment (and the main reason my plate is about to be removed).

So I'm calling an audible. The bolts can be reused, they should be clean and dry and follow the 56 N·m plus 90% rule and they should last a few reuses before they loose enough strength that they don't hit the design clamping force.

The problem with most of the cars on xoutpost is that most will not know how many times they've been reused already so are you one reuse away from the bolt breaking in half on a pothole ? You won't know until you hit the pothole.

Will the car flip over if you break a couple bolts ? Nope will the sway bar bang around and tap out Morse code at 110 dB if the back bolts come loose? Yes it will (experimentally confirmed).

The bolts are not mission critical but there is a fair amount of importance to the stability of the car tied directly to both the sway bar and the stiffen plate (important enough that BMW is quite specific to mention don't drive the car without the plate).

I can feel the difference in stability at the first pothole* when I drive without the plate installed so there will be a lost of ultimate control if you leave it off not to mention a very large increase in the fatigue failure rate of the next in line parts that will now take up that strain by the absence of the plate.

* I can feel the front end wobble like the horrible feeling of a minivan, not as bad but there is a secondary shudder from the bent subframe springing back that works it's way back through the steering wheel.

Back to the 12.9 option which is the route I will be taking.

I have two 2001 X5s. They each have close to 170,000 miles and no repair history so the current bolts are an unknown. I want to retain the design clamp force because it makes sense for many reasons.

It's just too good of a coincidence that the normal use force of a 12.9 bolt is within 1/2% of the yield strength of a 10.9 bolt. It would be difficult to achieve a reliable force unlubricated but I'm confident that lubricated the bolts will achieve a reasonably close clamping force each use and I don't need to concern myself over keeping track of how many reused times.

The only thing I'm still curious about is the locking nut. I like the simplicity of the crushed to an oval style locking nut but I think that part of the reason for the exorbitant cost of the BMW bolts is that they are tapered at the end so you can start the nuts so I'm not sure what I'll do maybe just get 60mm vs 55 and use nylon lock nuts. On the other hand I'll be removing them at least annually to stay ahead of the inevitable old engine leaks so I probably won't need to have locking nuts on a 9000# force bolt.

So back to the 12.9 bolt option:

The 10.9 bolt is designed to apply 7531#, but when stressed to yield that comes to 9037#.

The 12.9 bolt is designed to apply 8979# at 80 N·m. (about 0.6% shy of the yield on the 10.9 bolt). To achieve repeatable clamping force lubricated is going to be needed and that drops the advised torque to 60 N·m.

I could add 1-2 N·m to the set torque to achieve greater than design but the simplicity of 60 I'm happy with 99.4% of design (especially since in reality there will be some variance and I would expect a +- of 300-500# anyhow.

So: to achieve a repeatable "9000#" clamping force you can either;

A) replace the bolts and nuts every time.

B) re use the bolts and follow the proper TTA process on unlubricated bolts up to an unknown number of times that needs to be experimentally derived. *

C) upgrade to class 12.9 bolts and use lubricated torque of 60 N·m (use 61 to achieve slightly more than design clamp force).

* I'll have literally a dozen original bolts for experimenting soon and will write a definitive article on the subject once I've tested a few bolts to destuction and learned roughly how many times they can be reused before they loose their holding power.

The study I quoted above I think used roughly 12mm bolts and 180° TTA which is a LOT more stretch (pitch of 2mm means 1mm of stretch on the bolt). At only 90° of angle on 10mm that means the bolt is stretched only 3/8 of a mm. It can likely be reused a LOT more times than the five determined in the example of the study.

I'm going to strain some bolts to destuction using 180° like the study first so I don't have to spend all day tightening 200x to get the bolt to break but get some solid evidence they have a reuse limit.

I would not be surprised to determine the bolts can be reused 10 times for example. Mine are approximately 0.3mm longer now and I'm curious how much longer they will get each use until they break. I'm hoping I can figure out a strain gauge to actually measure the drop in clamp force over time but I would be ok with deriving from the study that half the number of times to failure will be a good number for the reuse limit.

So: what we have learned:

• Bolts are definitely TTY using TTA (torque to yield, torque to angle), factuality proven by my bolt being 1/2% longer than new.

• BMW just like the study quoted determined that was the best way to achieve a reliable clamping force of approximately 9000#. (Factually derived from the yield strength of a 10.9 class M10 bolt)

• The M10-1.5 bolt is stretched about 3/8 of a mm past the pretension. (mathematically derived from 90° turn of 1.5mm thread pitch)

• After an unknown number of reuses (but quite possibly zero) my bolts are about 1/4 mm longer than they entered this world.

• clamping force based on dry torque changes a lot each use so TTA is a typical solution designers will use to get repeatable force in the field.

• the limitation with TTY is the bolt will self destruct over time. (It's just a fact that if the bolt is 1/4mm longer after each use there will be a limit of how many times you can do that)

• re-use capability needs to be experimentally derived and nobody has ever done this for this application. (But once done people can confidently reuse their bolts "a handful of times" without concern they will have any problems related to the reuse.

• M10-1.5 class 10.9 stretched to yield has the same clamp force of a 12.9 bolt at proof strength.

So the summary is: you can certainly achieve reuse using the TTA a couple times as the bolt will actually get stronger from the first stretch, but it's unknown how many times before the bolt no longer will supply the design requirements. I will go as far as to say I'm confident that number is greater than five and I will be surprised to find out it's less than ten. (Based on extrapolation from a 180° TTA lasting five reuses and this application using only 90° on a finer pitch bolt)

As I will be replacing all 12 of mine I will have a bunch for testing and will test to failure on enough of them to get some solid data for once again the only example on the web of an actual answer to something people have been pondering for two decades.

I have two bolts already off the car and may actually have time today to stress test one of them.

If you have been reusing them and just "snugging them" you have been compromising the handling of the car because the plate is a structural part of the suspension and provides perhaps 40-60,000# of cross brace force against torsion on the front subframe.

That said there is likely a 2:1 safety margin and if "snugging" the bolt provides "only" 7500# of clamping force vs the 9000# designed that is likely far more than needed to handle normal driving.

In a practice what you preach thought, I will be opting for using 12.9 bolts to achieve the design force without damaging the bolts and the simplicity of not needing to replace them. I don't want to compromise the design of the front suspension as I'm known to push my car pretty hard at times (well most times).

I found galvanized 10.9 bolts for under $3 which is a very reasonable price for a bolt you can start the reuse clock over with a known quantity. It might be as much as $4 with a washer and nut.

My thoughts on the idea of "just return under warranty" for a bolt that is designed to be single use is that is a consumable item and gaming the system do to the fine print working in your favor is cheating/stealing in my opinion. How is that different from an oil filter?

The bolt didn't "break" it did its job exactly as designed just like a used oil filter or oil for that matter. If you are ok with returning used oil under warranty then returning the used bolt should be in the same frame of mind.

I'm also very confident that the anecdotal "everybody does it" crowd have never researched the why and have been likely just "snugging" the bolts which is good news for the bolts because they will last a hundred reuses but they are absolutely compromising the handling characteristics, something that to me is the main point of BMW: it's their motto: the ultimate driving machine.

I'm going to try to set up a camera and take some video of the plate moving around when the bolts are loose to show people that in fact the plate is structural. If I can feel it in the steering wheel it absolutely moves.

Facts don't have feelings. If you disagree with me back it up with something and prove me wrong so I'll update my posts.

"Because they said so" is a shitty reason to replace the bolts.

"Because they are strained to permanent formation by design" on the first install, now that's an actual reason.

It's a reason, however to CONSIDER replacing the bolt and in my option laziness on the part of BMW to not have gone through the effort that I will do to determine how many times the bolts can be reused with near identical performance.

So as predicted, somewhere in the middle is the real world logical answer: the bolts can be reused "some number of times" and achieve design performance. They do not NEED to be replaced every time. That reuse # could be as low as 3 (the second time the bolts are likely stronger than new), but I'm confident the number will be at least five.

To install them, TTA must be used or you will compromise the strength of the suspension to some extent as you will have no idea how much less force is applied.

I want to call out @bcredliner for being a firm voice of reason even though it sometimes appeared to just be fighting words. Taking the side of follow the book led me to research that discovered the unknown "why" to a degree that will be very hard to discount.

You can note that @bc used common sense and researched examples like the Fastenal paper to back up his side, where nobody from the opposite side could come up with anything more than "because everybody does it".

It turns out that there is a solid amount of ignorance behind the just reuse it crowd, basically complete ignorance of using a bolt at yield to achieve a consistent clamping force. Not one of those "laughing mechanics" understand why the bolts are used as designed if they simply re-torque to a standard torque value. (Or more likely seat of the pants randomness because they only were considering the plate as a dirt shield)

To be clear my "side" was neither. I've been on a quest to find out WHY BMW spec is replace. I found the answer: Lazy*

It only took me a short amount of time to figure out a way to meausue the thread pitch on a used bolt to confirm with no doubt the bolts are deformed.

This changes the discussion from a completely uninformed guessing game to an informed decision and now becomes a discussion of how many times are you comfortable with reuse or do you decide to not tighten fully and live with the reduced capability of the suspension that will not be as rigid.

*BMW was lazy to not spend one hour to determine how many times that bolt can safely be reused. I'm betting on "more than ten" which would be enough for most cars' lifetime. They could simply instruct in the repair manual to add a dent in the plate with a center punch any time the plate was removed to keep track.

There's absolutely no reason the bolts would NEED to be replaced. (At least every time, possibly ever). A proper non wasteful solution would be to KNOW how many times the bolts can be reused and keep track. That wasteful thinking is what bothered me. Reduce reuse recycle. I'm a person that fixes shit vs replace it like the door handle carriers and the door actuators. It's not just about the $ it's about the carelessness of sloppy use of resources.

Several kg of aluminum and steel now aren't going to a landfill and don't need to be mined now because of the three DHC and actuators that I repaired vs replaced. The replace vs repair mentality today is one of my biggest gripes of this world.

Some people may not believe my conclusions but I've been at this problem solving game a very long time I'm very good at it. Prove me wrong or your point is mere speculation. Facts have no feelings. "Just because" is no better a reason to reuse these bolts vs "because BMW said" for the case of always replace. Either side is guessing.

I've done enough research to conclude that under normal circumstances, a bolt can be reused TTY numerous times as long as the required forces aren't too close to the yield strength. I will make the case that these bolts are in the class "normal circumstances" and can certainly be used some unknown number of times.

Once I test to failure a few bolts to determine how many times it takes then I can extrapolate a reasonable number of reuse cycles. At that point people can be informed and decide how many times they feel comfortable with reusing them.

Before even performing the test I can say I personally would be comfortable with five uses based on the 1/2" bolt with 1 mm stretch lasting five uses and the 10 mm bolt only being stretched 3/8 of a mm past tight. The preload is much higher on the M10 (like 45 vs 15 ft·lb) so there is some stretch to the bolt from pretension. Clearly the bolt is stretched more than 3/8 of a mm under load to end up about 1/4mm longer or it's been reused a few times.

My guess is ten that's why I said five reuses is a safe bet.

I may have to revise that number after my destuctive testing but until then I'm sticking with five.

Make sure to use washers on the aluminum side to spread the 9000# force, aluminum is on the order of 30-50ksi vs the steel being 130ksi.

I don't even think it's critical to use galvanized in the land of salt and cold if you take the replace with cheap bolts route. It will not be difficult to remove once rusted and that will act as a locking feature as a bonus.

I appreciate your comments. It's difficult to determine intent in writing. I apologize for anything that seemed confrontational. I think it is great that you are willing to do some testing to see if you can find some support for making either decision.

You guys talk about bolts and nuts. For my 2013 X5 E70, there are no nuts per se. All the bolts go directly to the subframe steel beams. Are these still TTY bolts? Thanks.

Without "tone" it can be impossible, but in this case as mentioned I saw only objective input. At times maybe a little more tight tolerance than the scope of DIY repair. Like I mentioned I'm looking for real world answers not 1% tolerance. In this endeavor the goal is to find out with a home brew test, what is a reasonable solution and if there is one.

I'm convinced I've found enough research from other people's testing to determine that it's absolutely ok to reuse the bolts at least a couple times.

There is literally ZERO info on the web that can give us a solid answer as to why, either way. In a way, @bc making the point that nobody that "just does" (reuse the bolts) never came up with any "how" to properly do that without compromising whatever reason that surely was there. This type of pushback just is rational thinking and I'm ok with that it helps me dig deep enough to find actual facts.

I may have missed something in my search without being hard-pressed to find proof.

I believe I have. The evidence will be coming soon.

Sooner than planned as it turned out: Lumba2 developed a horrible dry ball joint sound in the front end and I can't see where so plate coming off today.

https://uploads.tapatalk-cdn.com/201...3bb9f7e286.jpg

So: results!

I took the plate off my wife's car and it was certainly removed in the past as the front bolts came off with 45 and less than 20 ft·lb of torque!

The back four bolts took between 58 and 68 ft·lb to remove and that was inline with the results when doing repetitive testing at TTA.

So this is just a quick report because it's solid info.

I have to repeat the test with some new bolts.

So what did I discover?

• when torqued to spec (56 N·m + 90°) the bolt was 0.37mm longer, almost exactly the mathematical result of 3/8.

• when the tension was removed, the bolt was 0.08mm longer, which is inline with if my earlier example was reused 3-4x in the 18 years.

• using 56 N·m preload the bolt didn't stretch even 0.001"

• the first re-tighen (of MY doing) the bolt took about 103 N·m to get to yield

• each successive re-tighen it took about 3 N·m less (103 100 97 95 92)

• I could really feel the drop off in force by the 4th attempt so on 5th time I decided to twist more than 90°

• there was virtually no increase in N·m torque to go between 90 and 120° then BANG! One bolt becomes two!

I need to test a new bolt but it looks like I was VERY CLOSE to the five use estimate.

The first three re-tighen tests I could really feel that the bolt was fighting me it took increasing solid effort the full 90° swing. The last two I could very much feel the drop off in resistance and were definitely past useful life.

I have no history on these bolts so don't know how many times they've been recycled but at least once.

At this point I would very confidently use them 3-4x without a question, they felt just the same during the torque to angle, but i have to see what the results are with new bolts.

I was thrilled when it popped. It may have gone 5 more cycles if I stuck to 90° but I'm behind schedule I have to wrap things up.

If you use a digital torque wrench like me you could also feel for the yield zone. If the bolt (dry) yields above 100 N·m it's not past it's useful life in my determination. If you can't get 95 N·m at 56 + 90° it's shot I would not use that bolt.

I will do a complete write up and also I'm planning to use 12.9 bolts for my cars and will of course include the findings there as well..

So the short summary; re-use? Yes, until dry torque at 90° is less than 95 N·m (I may be revising that # down or up after I get new bolts to repeat the experiment.

"My thoughts on the idea of "just return under warranty" for a bolt that is designed to be single use is that is a consumable item and gaming the system do to the fine print working in your favor is cheating/stealing in my opinion. How is that different from an oil filter?"

NO "gaming the system" as FCP even says you can essentially do oil changes for life for free, including oil filter. That's their deal and that's what they sell. No "gaming" just abiding by what FCP sells. That's why some have suggested buying the bolts from FCP and returning them for refund when replacing. That's what FCP sells. LIFETIME WARRANTY on everything they sell.

Stiffening plate removal / reinstallation
 

I guess like "free shipping" fcp has to decide what items they can sell without losing money like those as an example.

If FCP it ok with it that's just very unusual but if it's a loss leader to get you to keep you coming back good on them. I may have to check them out.

I just did check 'em out and I stand corrected they do literally say "even the parts that wear out".

Nice thanks for pointing out the craziness of FCP.

Bought a new turbo for my A4 from FCP, $1360. The wastegate pivot is a known weak point, they sometimes fail as soon as 40k miles. FCP assured me they would replace it no questions asked. We're eventually going to find out.

The only thing most peoples like myself do when reusing the bolts and nuts is that we just tighten them with an impact and forget about the 90 degree additional turn.

1+,

I tighten to 56 N·m + 45°.
That is good enough for me.
The 90-degree thing may be too much, actually 56 N·m + 90°) will bring the torque to the same as a typical wheel lug, which is usually M14, not M10.

Anyway, for me, it is 56 N·m + 45°...
I have done this several times, maybe 4-5 times, zero problems.

To what torque is the problem; completely randomness with 'impact'; somewhere between 20 and 100 ft·lb. My wife's six bolts ranged from about 20 to 68 ft·lb to remove (the properly torqued when tested were within about 65-70 ft·lb to remove).

The preload of 56 N·m will be plenty for the purpose of the anti-sway bar, but will not do a great job of holding the plate against shear (BMWs main purpose of the bolts/plate).

I'm going to do a test of what if any motion on the plate when the bolts are not torqued properly.

The corner mount is not just a plate of steel to aluminum; the bolt hole on the frame is a solid donut of steel about 1.5" in diameter and 1" thick welded to the corner of the subframe on steel plate about 6mm thick; it could easily handle 20,000# of diagonal force.

I will examine my wife's anti-flex plate when i get back home; one side was very loose and if there is any concern of does it move, it should show an oval wear where the aluminum slid over the steel donut. In addition My car I used 'seat of pants' or maybe i used 60-70 ft·lb straight torque to put them on (I would have looked up the standard torque of 3/8 or M10 bolt), so i will likewise examine mine for motion wear.

I also plan to tighten the bolts to maybe half normal clamping force and put the car through some stresses that should move the plate; i'll take video to see if it actually moves and determine if there is any need to even worry about it.

Also, I was thinking along the same idea above of pre-load and 45°, it may be a very good way to get a semi-consistent clamping force, but in reality, lubricated straight torque will likely be better; i will do some tests with the 45° concept shown above; i don't think that will achieve a consistent clamping force, because each bolt will have different cross section and hardness each re-use.

Case-in-point when i put wife's bolts back in on the back to hold the anti-sway bar, i used 56 N·m + 90° to tighten them, and measured the torque required to get there; the first two averaged about 105 N·m which matched pretty close to the one i tested to failure, but the 3rd took about 110 N·m and the forth I got to about 117 N·m before i even got to 90° and it was still climbing. (i'm betting that bolt actually was replaced so that was the 2nd use).

I think there are two reasonable re-use philosophy options;

1: use a lubricated straight torque to a value less than yield, that will get a reasonable percent of design clamping force, say 80% and that will not require replacing the bolts really ever.

2: keep track of how many times re-used and use them 4 or 5 times before repacking; if you have a peak-reading torque adapter, replace any bolts that get below 97 N·m during the 90° tightening phase.

(those values are preliminary).

I don't know what bolts are used on 2013 X5s. Sorry.