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Suspension thump !!!
My suspension consists of GC Koni D/A coilovers with Eibach springs, Racing Dynamics front and rear sway bars, and Kuhmo MX 255F/275R 17's. I have 30k miles on the '02 M Coupe. The thumping noise started two weeks ago. It's caused by the RIGHT REAR tire only. Whenever the tire goes over any uneven surfaces, I feel and hear thumping sounds. It's not metal to metal, in fact it sounds like the surface that it is hitting might have rubber or padding material on it. On smooth freeway surfaces, there is no sound. On uneven freeway surfaces it comes out quite a bit, as the suspension oscillates. On city streets, it comes out the loudest and most often. It doesn't seem to affect the car's handling at all. My mechanic took the car out on two separate occasions and checked the suspension thoroughly, and determined that the shocks and the RSM are fine, but so far he can only guess at what it might be. I am hoping to gain some insight from the gurus. Please help.  TIA  | | Reply » Suspension thump !!! |
Quote: My suspension consists of GC Koni D/A coilovers with Eibach springs, Racing Dynamics front and rear sway bars, and Kuhmo MX 255F/275R 17's.
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Your mechanic already checked the suspension thoroughly, however I would take a quick look at the sway bar mounts on the rear control arms. This mounting point is a weak area on the control arm and really should be reinforced if running the Racing Dynamic sway bars.
http://bimmer.roadfly.org/bmw/forums...4058961&page=1
| | Reply » Suspension thump !!! |
I have the same setup. Although I have a constant thumping and banging at low speeds, I would check out the rear shock mounts if not GC or equal and Swaybar attachments both sides and wether it has shifted left or right. My springs have always made a bunch of racket on their mounts, no matter what I have tried.
as a side note: I had to remove the GC rear adjusters to get the car down where it belonged. I use round Delerin Washers made from 3" round stock the get height adjustment.
MarkL
| | Reply » Suspension thump !!! |
Quote: Your mechanic already checked the suspension thoroughly, however I would take a quick look at the sway bar mounts on the rear control arms. This mounting point is a weak area on the control arm and really should be reinforced if running the Racing Dynamic sway bars.
http://bimmer.roadfly.org/bmw/forums...4058961&page=1 |
Good point, John. Knowing about the RD problem, was reinforced and checked for origin of noise.
Thanks,
Eric
| | Reply » Suspension thump !!! |
Quote: I have the same setup. Although I have a constant thumping and banging at low speeds, I would check out the rear shock mounts if not GC or equal and Swaybar attachments both sides and wether it has shifted left or right. My springs have always made a bunch of racket on their mounts, no matter what I have tried.
as a side note: I had to remove the GC rear adjusters to get the car down where it belonged. I use round Delerin Washers made from 3" round stock the get height adjustment.
MarkL |
Hi Mark:
We both know about the 'normal' noises that our aftermarket system makes. However, this thumping noise is 'new'. I am sure it was there before, but during the last two weeks, it really 'came out'.
My RSM are from GC, still, I had it checked, and that wasn't the problem.
The sound is not metal to metal. I had the rear bar attachment break on me a few months ago, ( the passenger side ), had both sides properly welded. When it broke, it made a clanging sound, unlike this.
Thanks for your input.
Eric
| | Reply » Suspension thump !!! |
Which Eibach coils do you have... are they from GC with their perches? And do you have any sense of how much suspension travel is required before you get the noise?
Depending on the coil, and the orientation of the coil on the perch, it is possible for the coil to tip and become partially mis-seated on the perch. When it pops back down, you hear a dull thud... not nearly as sharp of a sound as you might expect.
The perch rings have a inner flange, and on the original design the top edge of the flange was flat and it was possible for the coil to hang up on it. Their newer perch rings have a chamfered edge on the flange which is to help the coil to properly re-seat.
Other things to look at...
- muffler mounts... my dad's old 320iS made some thumping noises when he lost on of the rubber donuts that secure the brackets to the chassis
- sway-bar brackets and mounts... check both ends carefully as well as the bushings towards the center.
- stuff in the car... are you sure it's not something in the hatch moving around?
- gas tank straps... (someone's gonna have to help me here)... I recall some people have noises resulting from something around the gas tank, but I don't recall the specifics.
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Suspension thump !!!