Quote:
Originally Posted by upallnight
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.
|
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