Quote:
Originally Posted by MooMooM2
Been tracking down a noise and thought was one of the pulleys, replaced one and noise was still there, should have just have replaced all pulleys and belt while I was there. Now pretty sure its not a pulley but the belt since spraying a bit of water quites the noise)
So started doing it today, almost all done (not bad job, no space in there but very DIY). When I ordered the parts I did not even think about bolts and the whole single use BMW bolt thing. I have installed with the old bolts (they have 32k) and torqued to spec, seems fine. Have to finish the job because I do have somewhere to go next weekend and don't want to be finishing this job too close to it.
Bolts are steel, am I overthinking this? Should I just finish up the job and that be it or should I replace the bolts in a few weeks when I can?
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If the bolts were torqued and yielded (torqued to a spec like 80 ft-lbs for example, then add an extra angle twist to it 90 degrees to stretch the bolt), then you need to replace them. This is because once a bolt is stretched, it is permanently deformed as it has gone past its elastic deformation stage and into plastic deformation making the deformation irreversible. This means the bolt is now stretched and it can no longer provide the correct clamping force that bmw expects when they calculated the torque + stretch angle, also the bolt once it has gone plastic is now weakened and if you try to stretch it again you risk snapping or shearing the bolt. This is a huge PITA because now you have to remove a broken bolt that could be stuck really deep inside of a hole which is never fun. So imo always replace single use bolts.
If you must reuse a bolt, just apply the torque and don't yield it. So maybe do half or 1/4 of the stretch angle and leave it at that until you're able to replace the bolt.