mpotvin

I have a 1991 C4 with 60K miles that I bought a few months ago. I've had everything gone through from one of the best alignment/suspension shops in Seattle (Truline). They just installed a PSS10 kit, corner balance, alignment, etc. checked all of the bushings...everything looks great. I now have a very noticeable rubbing/vibration/loud noise coming from both the front and rear of the car when I am turning, but the wheels/tires are not touching anywhere. The ride height is set at euro ride height, 205/45/17 fronts and 225/40/17 rear tires. Could it be the Diffs? anyone run into this problem before? I would love any advice or suggestions you might have. Thanks, Mark

joey bagadonuts

Is this the first time you used these tire sizes? Typically, you'd run 205/50/17 and 255/40/17 on a street 964.

Unlike the C2, the C4 is sensitive to OD's and the stock spec is closer to 25". The tires you're running are 24.26" and 24.09" tall. While the difference, front to rear, seems to be acceptable, I experienced problems with my C4 when I used a relatively short front tire.

Any way for you to try a set of wheels with tires closer to the stock spec? That way, you could eliminate this variable as the source of vibration.

jimq

check your power steering fluid level

mpotvin

Thanks for the advice, my fronts are 205/50/17s, I missspoke and rears are 255s. I'll check my PS fluid but just had everything refreshed when I bought the car....will check it again. Anything else????

Mrmerlin

plug your tire sizes in here see what you come up with its best for all of the tires to have the same diameter
http://www.miata.net/garage/tirecalc.html

mpotvin

This isn't a tire problem. I'm using the same tire and wheel combo that I had before the suspension change. Maybe it's just bad timing.

tbennett017

Its a long shot, but when I lowered my C4, I had a rub in the front wheel well when the outside wheel was loaded in a corner. It turned out to be the body work rubbing on the tire shoulder. It was not the fender arch, but up front where the fender meets the front bumper cover. There is not much clearance with the car lowered. I simply got rid of the extra sheetmetal flange inside the wheel arch that was rubbing (less than 1/4 inch) and its fine.

Even if that's not it, do your tires show any evidence that can help you diagnose the issue?

joey bagadonuts

Wheel bearings? If you're still on the original bearings and your car has covered a fair bit of miles, they're probably due for replacement. And, possibly, the new suspension is simply shedding light on this issue.

mpotvin

We've checked tire clearance and nothing seems to be rubbing, lock to lock. There's no apparent wear on the tire shoulder either. Truline checked the bearings (original 60K) and said they were in good condition. Seriously scratching my head. I'm taking it over to Akers Porsche to see what they can diagnose.