I can feel every bump..

[Dominic123]

I have a 2004 C4S with 90K; lowered with Bistein PS9; I have adjusted the front knobs for soft/firm and for the last 6 months can feel and hear every bumps; are the shocks bad? The kit has only been on for approx 40K miles; its like the are no shocks and every bump of dip in road its like its bottoming out.

I can hear the noise and its like bam bam etc.

Do I need to re pressurize the shocks?

Went to dealer during oil change and told them; the said eveything looks great..

[perryinva]

How low below stock are they adjusted for? Have you checked to see it the spring perches have lowered? You may be bottoming out on the bump stops in the rear. There is only a 5mm range of correct height in the rear and 20mm in the front. Some people assume because you can adjust the spring perch anywhere on the coilover, that they will work where ever you put them.

[judgejon]

raise the car 1/2" all around and see what happens....

[Loren]

raise the car 1/2" all around and see what happens....

Don't forget you will also likely need an alignment after doing that - which is also a good time for an inspection.

[wross996TT]

As already said, likely you are hitting the bump stops. You are too low for the coil overs.

[perryinva]

He stated he's had the kit on for 40k miles, but it's only been doing it for the last 6 mos, so that is why I assumed the perches may have loosened and lowered over time. If he's been on the bump stops for 40k miles, then they will surely need a rebuild. Hope he gets back to us. They never seem to, though.

[Dominic123]

Thanks for all your help; sorry about not getting back sooner; have not had the time to drop off car.

Maybe it is on the bump stops; I did pay $500 for a GT2 alignment about 6 months ago and thinking maybe with the adjustment they set it close to the bump stops; they set it to a certain rake from front to rear.

Not sure if I should set it back to factory alignment or the GT2 alignment specs?

[perryinva]

Thanks for getting back! Yes, you should have mentioned that part, if they adjusted the rake, F-R, then they HAD to adjust the perches. It is the only way to do that. They have adjusted you too low, and you are hitting the bump stops. If they do not know how to check the correct settings for height adjustment of the coilovers, defined by Bilstein, then they need to get the installation instructions. You can NOT just choose a height you want to adjust the car to and set it there. The PSS9s or 10s do not work that way at all. They correspond to roughly x73 or x74 ride height. GT2 or 3 is too low. There is a specific 5mm adjustment range that is correct for the rears and a 20mm range that is correct for the fronts. For the fronts, you measure from the center of the clamping bolt (that clamps the coilover to the carrier) to the bottom of the spring perch. The distance must be between 100 and 120mm. This ROUGHLY corresponds to 25" to 25 3/4" measured from the ground to the top of the fender well through the center cap. For the rear, it is from the bottom through bolt to the lower spring perch and must be between 185 and 190mm, which is roughly around 25 1/2" at the rear fender. Adjusted Anywhere else and you lose the full range of the shock travel and risk hitting the bump stops, as well as being outside the range of where the helper springs are fully compressed and the main springs under correct tension. The manual can be found here: http://www.renntech.org/forums/topic/26075-bilstein-pss9-install-instructions/

Pss9 and Pss10 are near identical except there is one more adjsutment on the 10 and on the PSS9, 9 is soft & 1 is stiff. On the PSS10 1 is soft and 10 is stiff. Go figure.

[Dominic123]

Thank you very much for that detailed answer; its going back in next week to have it checked; maybe I need to go back to factory settings with the P9 instead of the GT2 specs.

Will post once issue resolved.

Thanks again for all the help and advice.