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      02-14-2013, 05:07 AM   #20
HighlandPete
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Drives: BMW F11 535i Touring
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Quote:
Originally Posted by Daveyc View Post
Not a good outcome, I'm afraid. I went up to the dealer and took one of the technicians out for a drive first thing this morning. He agreed completely about the noise - in fact, he heard it before we even got off the dealer premises when we went over a couple of quite abrupt speed bumps. We got onto some backgrounds and the guy could clearly hear that all four dampers were involved in the percussion party (nearside rear being by far the most easily provoked). I left the car with them, as agreed, and the head technician then spent some time with it, including back-to-back road test comparison with another car with adaptive.

Guess what? The head techie decided that my car was perfect, with no unusual noises........


This is a techie comment, but I've played with suspension on a few cars and bikes, and I think this is a case of the dampers being significantly under-damped on the rebound stroke (no problem on compression), resulting in them over-extending and hitting the end-stops at times.....
Sounds the typical response when the garages don't know what is wrong. There is clearly nothing obvious.

I'm not sure this is exclusively an adaptive issue, (but could be in this case) as it appears some of the F25 1-series users have had rear suspension issues and clunking sounds. And not tied to adaptive suspension. Just this past couple of weeks it seems BMW are sorting it, after many months of drivers waiting. Have read the solution is with dampers, top mounts and bushes, (possibly revised).

Also I've read of some rear suspension thumping noise on 5GT models, again not directly linked to adaptive suspension.

I understand your thinking, but I'm not sure you really get to the endstops, that would be some pretty aggressive dynamics and you'd be tossing the car all over the place to lift off the wheels. You can't rule anything out, as it is all supposed to be in tolerance. But how you describe it, in an aging setup I'd be looking at loose top mounts with the clonking you describe.

As you appear to have the same/similar clonking front and rear the common 'parts' are, from my thinking, damper internals, damper control (software/sensor related) and wheel/tyre combination. I read that one 1-series user rid his car of the rear clunking when he changed wheel sets for winter use, 16" moving to 17", so some very unusual suspension behaviour involved in that case.

I do tend to agree the issue looks likely to lay with faulty dampers, but 4 on one car makes me scratch my head. Possibly some control module common to damping strategy may be involved. One bit of thinking... as if the rebound valving is slow to respond and goes to full closure, too late to cushion the rebound, but makes it abrupt with resulting clunk. Vertical motion sensing faulty?

Has you dealer opened a PUMA case, or at least checked with BMW for others with the same issue, already on record?

HighlandPete
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