Stiffening plate removal / reinstallation

[andrewwynn]

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.

[andrewwynn]

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.

[crystalworks]

Originally Posted by Attacking Mid

AM.

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.

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.

[EODguy]

I see my work here is done...

Sent from my SM-A730F using Tapatalk

[Fifty150hs]

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.

[bcredliner]

Originally Posted by cn90

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.

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.

[bcredliner]

Originally Posted by crystalworks

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. Yes, the burden of proof is on anyone that claims the bolts should be used or not used. You have given your input as to why they can be used. I have challenged your explanation as assumptions without a basis in fact. And I have said if you don't know why BMW engineers state not to reuse the bolts and what happens if you do then anything other does not prove your point.

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.I am not challenging anyone's talent, knowledge or integrity. I am challenging how they arrived at what they say is a conclusive decision. I am not claiming the bolts should be reused or not. I have said many time I don't know. There is nothing for me to prove.

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

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.

[bcredliner]

Originally Posted by Fifty150hs

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.

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.

[bcredliner]

Originally Posted by oldskewel

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.

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

[Fifty150hs]

" 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.