kdurg

I have a '96 C4S....when I bought the car with 42k on it....it had a nasty front end vibration felt in the steering wheel between 65-70mph.

P-dealer indicated tires were "cupped" and that this is normal on a staggered wheel setup due to the inability to rotate tires.

Ok..so I go out and drop $1200 on all new rubber at all 4 corners. Hoping this will correct the problem.(Michelin Pilot Sports)

Dealer does speed balance and mounting along with complete alignment. Vibration is minimized greatly...but is still evident between harmonic range of 55-60mph.

Now after more than 500 miles on new tires...the vibration is back nasty as when I originally got the car.

Tire pressure is set correctly ...

Any ideas ?? Dealer says rims are not bent....I am clueless as to what else could me causing this problem ? Steering rack issue ??? Or is this an inherent problem with AWD on this car ??? Any of you C4S owners experience this problem ?? Or do I have to speed balance the front end once a month ?? HELP !!!
THANKS.

Randy M

It could be warped rotors. Has anyone mentioned that yet? I have had my car aligned at two independents in the last year. The second time I had it done was after having my rear hats installed. He mentioned to me that my front end alignment was way out of spec from the first alignment I had done 6 months prior. Do your research in order to find a solid independent shop to do the work on your car. Just because its a dealer that did your work does not mean that they are the best shop in your area. I am lucky to live where I do because I have one of the best in my backyard. Check with your local chapter of the PCA. They will give you a good idea of some reputable shops in your area.

4X4SCHE

This sounds exactly like warped rotors. I had the same problem. I rebalanced the wheels and the problem got better, then it came back. The effect of warped rotors is apparent even if the brakes are off. Swapped the rotors for new ones.....problem solved.

kdurg

I did not disclose.....rotors and pads just replaced last week....vibration still apparent.
Keep the ideas coming....I am a perfectionist...like most P-Car owners...I can't deal with the vibration......

THanks

johnt53

Tire pressure is set correctly---but to what pressure? To Porsche owner's manual specs? Some members have reported a better ride with settings lower than recommended--i.e., 32 front, 34 rear.

911

What type of alignment did they do? Did they set everything back to factory specs (i.e. toe in/out, camber, etc). Has the car ever been corner balanced? Actually, I'm not even sure if that would resolve your problem because it seems as if your condition intially went away, but then it came back.

The only thing that comes to mind is tire pressures (perhaps there is a slight leak?). When my '86 Carrera drops a small amount in tire pressure it's VERY noticeable. Or, maybe there is an error with the balancing of the tires?

Is there a suspension specialist in your area? I have little confidence with the local Porsche dealers near me, so that's why I'm asking.

Rich

Viken

Warped rotors are not going to cause this unless the vibration happens during braking. Assuming wheels and tires are true and not out of round, tires do not have shifted belts, this could be caused by worn bushings somehwere in the A-arms or elsewhere in suspension parts.

Frank 993 C4S

I had the same problem in the 60 - 65 mph range when I initially got my car. Solved it two ways: 1) went for an alignment at a reputable 993 specialist and 2) had my rims checked (refinished and rebalanced) at Wheel Collision Center in PA. Took care of 95% the problem. When my tire pressure drops to about 32 psi, the vibration comes back so I keep it at 36psi. I figure that replacing the tires next Spring will take car of the remaining 5%.