Single use suspension bolts

[18BSMF82]

I was told that suspension bolts are single use. Is this true? I am planning on getting new springs installed and wondering if shops usually reuse suspension bolts or should I pay them to use new ones...? What have you guys done when replacing springs?

[horsepower_and_hounds]

Garbage....... Believe it if you want then spend your money On my first M4 I changed suspension 3 times and never replaced bolts. On the M2 two times and on this M4 going on its 4th. At most if your worried put a dab of 242 on it and call it a day

[dvq]

Originally Posted by 18BSMF82

I was told that suspension bolts are single use. Is this true? I am planning on getting new springs installed and wondering if shops usually reuse suspension bolts or should I pay them to use new ones...? What have you guys done when replacing springs?

The technical service manual does indicate much of the hardware is to be replaced, they factor in deformation for correct torque. I personally reuse hardware indicating renew — but I replace anything that has torque to yield values. For example, almost all the bolts on the carbon brace or aluminum brace are marked as replace and I reuse those, however the nuts holding the strut to the shock tower are 30Nm (or 56Nm if you have m10) + 90 degrees — those I replace.

By design TTY bolts are no longer as strong as they were before stretched. They can't provide the same clamping force as before and could break.

[TopJimmy]

I'd go with what Hounds said. IMO only bolts with a TQ spec plus some kind of "extra turn" should be replaced. I just examine my bolts well, and pay close attention to how a bolt "feels" during removal and re-torque down.

If something grabbed tight when loosening, but spins on easy now...eyeball it good. Even more important for the opposite.

If a nut/bolt has a high TQ spec you should feel for stretch or pull against the threads. Anyone who has snapped a bolt or pulled a thread should remember that weird feeling just before the failure.

[dvq]

Also to complicate things and my own judgement of what bolts to reuse and which ones not to — not all tty bolts have angle specs, and some regular bolts have angle specs. *shrugs*

[18BSMF82]

Thank you all for the responses. Seeing how the previous owner did the springs once already I think I will go ahead and order a new set of fasteners...more for peace of mind than anything else. Anybody know where I can buy some other than the dealer?

[irunalot]

Try getbmwparts.com they are a dealer but sell under retail. I've bought quite a few genuine BMW parts from them.

[ellipsis212]

Good advice above. I'll add that many of the lower torque bolts (say 25nm) can easily be stretched with just 5nm additional. Inspect threads on the strut top hat bolts and the brace bolts if you're going in there.

Also alignment is fiddly. I'd personally wait until the next one is due to replace any suspension bolts a few days prior.

[horsepower_and_hounds]

Originally Posted by 18BSMF82

Thank you all for the responses. Seeing how the previous owner did the springs once already I think I will go ahead and order a new set of fasteners...more for peace of mind than anything else. Anybody know where I can buy some other than the dealer?

Your $....as long as you sleep well at night

Originally Posted by irunalot

Try getbmwparts.com they are a dealer but sell under retail. I've bought quite a few genuine BMW parts from them.

Good recommendation...also FCP Euro has pretty good pricing

Originally Posted by ellipsis212

Good advice above. I'll add that many of the lower torque bolts (say 25nm) can easily be stretched with just 5nm additional. Inspect threads on the strut top hat bolts and the brace bolts if you're going in there.

Also alignment is fiddly. I'd personally wait until the next one is due to replace any suspension bolts a few days prior.

All true but if you torque....you torque and the bolts are fine for reusing over and over. Not going to argue why..... just that 95% spend their money smarter

[Racer20]

Torque to yield bolts need to be replaced. That's well established, so I won't get into it here. But there are two other factors that might dictate replacement:

-bolts with locktite-type coatings

-bolts with anti-corrosion coatings

In both cases, the coating integrity won't be the same the 2nd time so the bolt needs to be replaced.