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odd tire looks/wear - help request

Hi,

I have Dunslop Sport A2 tires on my bmw 318i. The rear passenger side one looks rather odd. Although inflated to about 2psi over its suggested pressure, the center of the tire looks as if it is cupped continuously around, so that the outside tread contacts the ground while the center does not. Of course under weight it contacts fine, but when off the car, I can easily see it. However, additionally, this tire is wearing more than the others. Despite this 'cupping' pattern, the center of the tire is actually worn more than the outside lugs, and worn more than the center treads on the other three tires. I do have slightly higher presure, but that has only been for the past few weeks, before that I had it exactly per spec. Any information on why this may be so, or how to fix these problems would be great. Do some tires just go bad like this? Thanks,

JMH

Reply to
JMH
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Yes, sometimes tires go bad (missed something in quality control) but most likely you have a loose axle/wheel bearing, worn bushings, misalignment, etc. Check everything else before you go back to the tire.

Pete

Reply to
pete selby

Approximately 10/11/03 10:40, JMH uttered for posterity:

It could be a bad tire, would think you could feel vibration from it on as lightweight suspension as a bimmer. More likely you may have a bad rear suspension component, starting at the shock, then the axle joints, wheel bearing, or not too likely a grabbing brake. If you rotate another tire and it develops the same wear pattern, it is the suspension. However, if that worn tire is rotated elsewhere, the existing abnormal wear may continue.

Reply to
Lon Stowell

The cupping could well be a tire balance issue and/or a worn shock absorber issue. You don't necessarily have to "feel" the imbalance in your nether regions for a tire to actually be out of balance.

The wear down the center of the tread is normal for a tire mounted on the rear of a rear-wheel drive car. The radial design and belt "pull" the tire tread into distortion as acceleration and decelleration torque inputs are applied. Being the right (passenger) rear, the tire is often the lightest upon acceleration due to axle torque, so it might tend to be the fastest-wearing tire on the car.

A tread-depth guage applied across the tread of the other rear tire will likely show that the center of the tire is wearing faster than the edges.

Front tires on a RWD car will usually wear on the outer edges first due to cornering inputs.

A religious rotation schedule helps tires to wear out more evenly in this situation.

Bob Paulin - R.A.C.E. Chassis Analysis Services

JMH wrote in article ...

Reply to
Bob Paulin

Thaks for all the great replies... One thing that I did notice last time jacking the car up was that as the car got lifted, the whole tire wanted to spin itself a bit forward, just as the load came off. Then, I noticed that I could shake the whole wheel/cv joint assembly about 1/4" rotationally, with the parking brake on. The whole shaft would move, all the way through to the flange at the differential. I do have a Limited slip diff, BTW, but it was just rebuilt, not 500mi ago, with BMW parts, as the bearings were bad, and they said that everything else was fine...

Any suggestions? Is something wrong? If so I should go back to have it righted, asap.

Thanks very much,

JMHG

Reply to
JMH

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