Originally Posted by HighlandPete
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?
Good point re adaptive versus passive - I jumped to the conclusion that there were more bits to go wrong on an adaptive setup. I agree with you completely on the sound pointing to worn or loose top mounts on an older car. I don't know if BMW checked to see if they were loose.
I was also wondering if this could point more to control software than dampers. As you say, 4 faulty units is pushing the boundaries a bit and it's a huge coincidence that Rich's clonking is also most prominent at the rear NS. It could well a case of control SW either holding the rebound damper valves wide open or being too slow to close them, as you say. I do think the compression side is OK, as if I hit a ridge (i.e. stepped rise with no drop after), the car rides it perfectly, with no hint of a clonk - just that satisfying, nicely muted 'thwack'.
I could be a bit over excited re dampers over extending. I'm just puzzled that the clunking only seems to happen when the wheels drop int a dip, or come off a raised patch. Maybe it is just some internal gubbins rattling around.
I talked to my very helpful and proactive sales guys (he's already talking about my next car in 18 months time ...) and he's going to pass on an email from me and see what he can do. The dealer did say they'd been in touch with UK head office to see if any similar faults had been reported and said there was nothing, buy I guess this means nothing that they have yet taken seriously.
Sadly, I can see this taking weeks or even months to sort out.