Stiffening plate bolts

[bcredliner]

Originally Posted by crystalworks

They are being reused for a number of reasons. Chief being expense, but secondarily you have availability.

Members considering reuse or not only have to read this thread. Though increasingly they are going to have to wade through these type of posts in order to find the data points provided. It is not necessary to post BMW's position each time a data point is added. We realize you will never see not changing the bolts as acceptable practice and are okay with it. Certainly not trying to convince you of anything.

Cost and availability have nothing to do with it being OK to reuse. That is rationalizing. It's not OK just because everybody does it.

This has nothing to do with what I do and I am not defending it. Even if I reused them I would be saying there is no proof it is OK to do so and all the rest of the crap about sample size--blah blah blah. I would love to hear information that passes the facts check.

I don't have a clue what is right. As I've said, my guess is it doesn't matter. I don't want to be right and the primary reason for my posts is hoping that someone will post new informations or preferably specs and reason for the bolts used and a low cost option that is exactly the same.

Seems clear folks aren't reading the thread or they wouldn't feel the need to ask the question again so any input is all new to them, not repetition. You or "we" are wrong if you think I will never change my mind. That's offensive.

[crystalworks]

Fair enough.

[cn90]

- Let's say BMW says nothing about these bolts, the best way to approach this problem is: is there any scientific evidence to support replacing the bolts every time? If not, re-use the bolts.

- To me, these bolts are no different than the wheel lugs.

- This has been a boring thread to be honest...re-use the bolts and move on...

[bcredliner]

Originally Posted by cn90

- Let's say BMW says nothing about these bolts, the best way to approach this problem is: is there any scientific evidence to support replacing the bolts every time? If not, re-use the bolts.

- To me, these bolts are no different than the wheel lugs.

- This has been a boring thread to be honest...re-use the bolts and move on...

I think you just made it longer and still boring.

[TiminIndy]

So, when I click on the link on RealOEM for 31101096987, I get a price of $3.53, but when I look at it on FCP, ECS, Turner, etc.., I get prices between $15-20. Would that be for all 6 bolts? None of the listings show it as 6 bolts, but based on the price, I'm hoping it is.

BTW, my 3.0i has build date of 9/06, and I have the aluminum plate. I believe that's the last month they made E53's.

[oldskewel]

Originally Posted by TiminIndy

So, when I click on the link on RealOEM for 31101096987, I get a price of $3.53, but when I look at it on FCP, ECS, Turner, etc.., I get prices between $15-20. Would that be for all 6 bolts? None of the listings show it as 6 bolts, but based on the price, I'm hoping it is.

BTW, my 3.0i has build date of 9/06, and I have the aluminum plate. I believe that's the last month they made E53's.

6 bolts is wishful thinking. Those bolts are not specific to the stiffening plate, so there is no reason for it to be 6 rather than 1.

If you're really going to pay that much for BMW bolts, to ease the pain, first look up prices on the 77mm-long versions - PN 33306783637. (over $100 list price for one M10x77 bolt with a large captive washer). After seeing that, $20 each will seem like a deal.

Or you could buy non-BMW M10x55 Class 10.9 bolts for a fair price. Or re-use like most others do, and torque carefully.

[DougPEX5]

My questions are:

If these bolts are stretched during the torquing process, will the nut still easily run the complete length of the bolt?

If they do, then they stretched back and are ok to reuse?

If they stretch and stay longer, the nut would not easily run the length of the bolt, then I assume they are irreversibly damaged.

Makes sense to my engineering mind, but I only had a couple materials courses, and focused on electricity.

Maybe if I take off the belly plate I’ll try. Don’t hold your breath, I have enough on my to-do list.


Sent from my iPhone using Tapatalk

[oldskewel]

My post on this in another thread (#712 of the stiffening plate bolt threads):
https://xoutpost.com/1109289-post66.html
has some of the simplified concepts of yield stress, etc. as they relate to this issue. If you can follow that stuff, that's a good place to start.

Then with that as background, to try to answer your questions ...

Originally Posted by DougPEX5

If these bolts are stretched during the torquing process, will the nut still easily run the complete length of the bolt?

Depends on "easily." The deformation will be different on the bolt threads where they were contacting the nut. I've noticed on my own bolts that some seem to be deformed visually and by not threading back easily, and some seem like they did not deform at all.

Going back to the ".9" in "Class 10.9," that means the yield stress (where plastic deformation begins) divided by the ultimate tensile stress (where it snaps) is 90%. Everything has tolerances and safety factors, but if you really are in the yield region of a Class 10.9 bolt, you don't have much further to go (in terms of stress, although it can strain more since the yield curve has flattened off in that region) before it breaks. Given all that, I can see that they would not design it to yield "much," and maybe not actually at all. So I bet it is possible to torque it to spec and take it off and find that nothing actually yielded (proven by the nut finger threading the length of the bolt).

Originally Posted by DougPEX5

If they do, then they stretched back and are ok to reuse?

I'd say that yes, your thinking that easy threading over the full length means no plastic deformation actually occurred is a safe assumption. And in this case they can be re-used, perhaps even with the original torque+full-angle spec (but I'd go with a smaller angle).

Originally Posted by DougPEX5

If they stretch and stay longer, the nut would not easily run the length of the bolt, then I assume they are irreversibly damaged.

They are irreversibly deformed. But depending on just how deformed you're talking, I would not worry about it - and would re-install them as described in the other post.

I know this is a controversial topic so I try to be careful and write only things that are supported by basic theory. As others have said, unless we know exactly what the engineering reasons (if any) led to the TTY spec, it is at least a little dangerous to not follow the spec ...

Except in the case of the bolts themselves. Those (unless anyone has any information otherwise) are not special TTY bolts, or special or magic in any way. They are just M10x55 Class 10.9 captive washer bolts. I expect BMW uses them in non-TTY applications too.

You should be able to get exact non-BMW equivalents of those without any fear at all. Class 10.9 specifies the relevant material properties. You can match the coating if you like, in case you're one of the lucky few that does not have an oil-coated stiffening plate. And a loose washer would probably work just as well as the captive one.

One more thing - the nuts deform too, if the bolts do. So ...

[lincolnshibuya]

I wouldn't lose sleep on this, looking at mine they have been re-used several times and I even re-used them last time when I checked the under belly for leaks (PO disconnected the oil sensor before selling it to me... no lights OK..)

looking at it, if all 6 bolts say snapped out then what will happen next? the X5 will collapsed underneath because the stiffening plate is gone? what's the possibility of them all snapping together at the same time and causing an accident?

I've re-used nuts when the service manual says to discard them, I just put loc- tite on them and so far so good.

If it's part of the engine, transmission, differential, transfer case I would definitely follow the torque specs and use new nuts/bolts.

[bcredliner]

Originally Posted by lincolnshibuya

I wouldn't lose sleep on this, looking at mine they have been re-used several times and I even re-used them last time when I checked the under belly for leaks (PO disconnected the oil sensor before selling it to me... no lights OK..)

looking at it, if all 6 bolts say snapped out then what will happen next? the X5 will collapsed underneath because the stiffening plate is gone? what's the possibility of them all snapping together at the same time and causing an accident?

I've re-used nuts when the service manual says to discard them, I just put loc- tite on them and so far so good.

If it's part of the engine, transmission, differential, transfer case I would definitely follow the torque specs and use new nuts/bolts.

Is the reason BMW recommends not to re-use them because they will come loose?