Xoutpost.com - Stiffening plate removal / reinstallation

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Quote:

Originally Posted by andrewwynn (Post 1159118)

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.

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

Quote:

Originally Posted by andrewwynn (Post 1159126)

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.

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.

Quote:

Originally Posted by Fifty150hs (Post 1159173)

" 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.

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.

Quote:

Originally Posted by bcredliner (Post 1159174)

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

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).

Quote:

Originally Posted by upallnight (Post 1159175)

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"

Quote:

Originally Posted by X5only (Post 1159187)

I really appreciate your post. Thank you.

Quote:

Originally Posted by upallnight (Post 1159175)

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.

Quote:

Originally Posted by andrewwynn (Post 1159194)

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)Please see my post quoting the warnings. The stabilizer warning is separate and distinct from the fastener warning.

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.[COLOR="blue"]The method used to torque a bolt say nothing about the nut or the bolt. However if the TTA method is specified and it states not to reuse the fastener it is a strong indication the fastener is stretched or distorted to plastic deformation.
The bolt looks perfect but I have yet to measure the threads for distortion
[COLOR="blue"] In one of the links I posted it stated plastic deformation can be reached at as little as .0001. That is not something one can eyeball. 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. Again, TTA is a method. Unless you have the TTA specs for the second use there is no way to know if you have reached the clamping power specified. The testing is measuring the clamping power as they tighten the bolt. When that particular bolts reaches specified clamping power they read the torque. There is no way to do that when you are reusing a bolt.

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. You know that if you don't have the proper equipment to do testing there is no reason to do the testing. This is not something one can shade tree engineer. I don't know what the industry standards are for testing but I expect particular instruments are required and it is necessary to check many bolts to confirm the plus/minus range is very narrow.

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

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.