Disintegrated Bump Stops

[CamE32]

While replacing the rubber brake lines in the front of my 735i, I couldn't help but notice that the dust boots and bump stops on both shocks have completely disintegrated into little tiny pieces

What are my options?

Is this a dead giveaway that the shocks/springs are toast? Car has been sitting for ~5 years, but only has 44k miles.


I'm thinking a temporary fix could be cutting some new bump stops down the middle and then securing them around the shock shafts with large zip ties or hose clamps. I'm just not sure how much it compresses when going over large bumps and if the zip ties/hose clamps would be quickly destroyed.

[shogun]

That is normal after so many years that the bump stops and the dust boots disintegrate.
I have replaced them on front and rear, but for that you have to remove the shocks, you need a spring compressor for that. http://www.nmia.com/~dgnrg/page_27.htm
Might be possible to do a temporary fix as per your idea.

[CamE32]

I've heard shocks should be replaced after 10 years, regardless of miles traveled. Have you found that to be the case with the e32 7's?

I'm trying to budget the restoration, and I'd hate to needlessly spend $ if the shocks on my car are fine with only 44k miles. Might have to wait until I get it mobile to make that call though...

[shogun]

Probably depends on mileage and road conditions, not years. My 750iL now has about 175000 km and was built 11/1988, still original shocks installed, I only replaced the rubber/plastic parts like dust boots and bump stops.
But of course I have no real comparison with new shocks, maybe the drive feeling is different then.

[TheStigg]

I did a couple token FEA simulations for a regular bump stop vs. one with a slit in it. The boundary conditions and loads are a wag but the slit doesn't appear to make a significant difference. I say go for it with zip ties vs. removing the strut to insert a new one.

bump_stop1d.jpg
bump_stop1s.jpg

bump_stop2d.jpg
bump_stop2s.jpg

You can go back and check on it say 100 miles later to see if the ties are intact.

[CamE32]

I did a couple token FEA simulations for a regular bump stop vs. one with a slit in it. The boundary conditions and loads are a wag but the slit doesn't appear to make a significant difference.

Thank you for taking the time to run those simulations!

I say go for it with zip ties vs. removing the strut to insert a new one. You can go back and check on it say 100 miles later to see if the ties are intact.

I think I will end up going with that option for now. Hopefully it's not a waste of a good set of stops, but I think it's worthwhile to test it out.


I'm guessing it's a big no-no to drive without bump stops at all...

[SergeBMW]

I may do this too! Mine disintegrated as well, been driving the car without them but I dont think it would be detrimental to do so right? I assume this is only used in cases where shock travel reaches near limit?

[CamE32]

I assume this is only used in cases where shock travel reaches near limit?

I'm no expert, but my gut tells me this could accelerate deterioration of the strut if it's being slammed down to it's most-compressed state and hitting metal on metal at the strut tower (vs. hitting rubber with the bump stop installed)