Strange intermittent Thumping

[wastintime]

Hey everyone,

On the way to school yesterday, my car started doing something really odd. It's a '92 C2, and i heard/felt a thumping coming from the right rear wheel. I assumed I had a flat so I pulled over and checked it, but both rear tires were inflated to the same pressure I'd last inflated them to. The fronts were fine as well. My boss drove it around with me in the car and it wouldn't do anything funny. Today I drove the car again and it immediately started making the thumping. I couldn't get it on a lift, but the CV boots look intact, and it doesn't really feel or sound like a wheel bearing that's going to me. It's definitely coming from the right rear, and it increases with road speed but not engine speed.
I was just wondering if anyone's had any experience with something like this before.

Thanks,
Andrew

[Jeff]

I would start by checking the lug nuts on that wheel and then check the bolts where the half shafts connect to the transmission.

Let us know what you find.

[campbellcj]

It sounds like possibly a flat-spotted tire. Have you locked up the brakes recently, or did the car sit parked for a long while?

One easy way to check if it's the tire is to move that tire to another location on the car and see if the thumping moves with it.

[wastintime]

i know it's not a flat spotted tire, unfortunately, I wish it was, that's at least a simple non-mechanical problem. The car has ABS so it's pretty hard to flat spot a tire, plus I tried both my track and street wheels/tires and nothing helps the thumping. I did check the lug nuts, they're all fine, I can't imagine the axle bolts not being torqued since they were torqued Jan. 15th before a DE, but when I get it on a lift on monday I'll check.

[svandamme]

do you hear / feel anything when you turn the wheels when the car is jaked up and the gears are in neutral ?

could be bearings...

[surflvr911sc]

A rock or screw could be making noise as the tire spins. If a screw keeps a tight seal you wont loose pressure. Check that tire out really good before you go any further.

EDIT: also raise the car up and see if you have any movement while you are checking out the tire.

[wastintime]

Lol, well... shoot... you're right, there's 2 bolts in the right rear tire... I don't know what I was feeling with the other set of wheels, maybe that was just in my head. I almost think someone did this on purpose because there are two identical bolts in the wheel, and they're fairly big, like 15mm, I can't tell or back them out because their heads are worn, but and there is a washer on each of them. If these were my street tires I wouldn't care, I'd just get them fixed, but these are my track tires, I don't know if it would be safe to get them fixed... oh well, it was a cheap tire, and that might even be covered under the road hazard warranty.

[surflvr911sc]

LOL, BTDT, glad you found the problem and it's an easy fix.


15mm is huge! I would take to an independent tire shop and get their opinion on saving it or not. Good luck!

[onewhippedpuppy]

Missing any bolts from your last repair job?

[wastintime]

well, to make matters worse, the cheap tires I was so happy about finding for the track are discontinued, so now instead of needing to buy one new tire I need to buy 2 new tires 7 days after buying the old ones... man that sucks