Must all four tires match?

Dear Car Talk

Dear Car Talk | Sep 01, 1991

Dear Tom and Ray:

About 10 months ago, in an emergency situation, I purchased two new tires to go on the rear of my '85 Honda Civic DX, which were a different brand from those on the front. Approximately four months later, I rotated these tires to the front of the car, and had them balanced. Now, at 40-43 mph, the front end of the car rides like it's rolling over a washboard, and at 65-70, the steering wheel shimmies. Is it because I used a different brand of a tires on the back? The Honda dealer said it could be bad belts in the tires, but the service station that sold me the tires said that if it were the belts, the problem would show up at all speeds. The service station also found no problem with the front end. They said I might need to have the rear shocks replaced. Short of replacing all four tires, do you have any suggestions for me?

RAY: Not really, Judy. First of all, the fact that you bought a different brand of tires for the rear makes no difference whatsoever. As long as they're the proper size, and you didn't buy them at a yard sale or something, the name on the sidewall won't cause any shimmying.

TOM: And the service station guy is right about the belts. If the belts in the tires were bad, you would experience the problem at all speeds. So that's not the answer either.

RAY: And since you say you've had the whole front end checked, I'd have to guess that the rear shocks are the culprit. Bad shocks won't make the front end shimmy, but they will cause tires to wear unevenly. And if your rear shocks were really bad, they would cause the new tires to wear out and be out of balance by the time you rotated them to the front. And, by the way, bad tires are much more noticeable on the front wheels, because the vibrations they cause are telegraphed right up into the steering wheel.

TOM: At this point, you probably need four new tires and at least two new shocks. You can try having those "new" tires balanced again, but don't be surprised if they're too far gone.

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