Stiffening plate removal / reinstallation

[crystalworks]

Originally Posted by bcredliner

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

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.

Originally Posted by bcredliner

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.

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.

[bcredliner]

Originally Posted by crystalworks

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.

If you mean common practice based on input here, which again is not a sufficient sample, I agree. Standard practice is a technical term. An example would be a standard practice in quality control. It is the only acceptable way to do something. Changing the oil at less than the recommended interval might be a common practice but it is not the standard practice. But that is nit picking.



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.

[oldskewel]

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]

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.


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.

[bcredliner]

Originally Posted by oldskewel

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.

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.


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]

[cn90]

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.

[bcredliner]

Originally Posted by cn90

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 length 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.

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.

[crystalworks]

Originally Posted by bcredliner

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?

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.

[andrewwynn]

Originally Posted by cn90

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.

This will only be the case if the bolt was never fully tightened. The bolts i've taken out and measured are ALL longer than they started and grew each time I tightened. (it will not look longer it's only 0.08mm longer per cycle or so). The picture i took above shows clearly that the bolt is 36.25mm long in the thread count that should be 36.00.

Tightening to spec 4 times plus an unknown times it was done on the vehicle took the bolt to internal failure and one more time broke it in half.

It will not distort below maybe 70-80 N·m which will net you about 2/3 of the design clamping force. Clearly that is enough to not cause cars to suddenly start flipping over, but it also is a lot less than design.

When i reused my bolts i looked up the advised torque for M10 class 10.9 and would have set them to something close to that (67 N·m spec).

Torque'd to normal spec should be ok in my humble opinion, but until somebody actually does the research to determine for sure nobody knows. if the plate moves a tiny bit under certain suspension dynamics that will affect performance to some extent. Is it something anybody will ever notice, that's clearly up for debate.

I like the idea of maintaining the design clamp force but not have to replace the bolts so i'm upgrading to 12.9 bolts to achieve that.

measure the torque it takes to remove your 'seat of pants' tightening, i would be curious; when i removed my wife's they ranged from 68 down to about 20 ft·lb, which I would regard as not nearly ok. (one was 45, also not ok).

[oldskewel]

Originally Posted by bcredliner

... 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?

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).

Originally Posted by bcredliner

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?

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.