I made a big mistake in purchasing 225/50/16 Cooper Zeon tires for my rear . Driving above 50 is a nightmare. The car surves violentely when I let off or push onto the gas. And at slower speeds it won't stay straight while shifting. Here is my question: Tire rack has Potenza RE050A 225/50/16 tires on sale right now. Does anyone know if these tires will return my S to that way it was before? Thanks?

 

Have you checked tire pressure? I think I'd start there.

 

No, I haven't. Could that be the cause of my problems? Any idea what it should be? Thanks.

 

If you are running different tires in the front and rear, this will cause handling problems.

Also, if you are replacing the OEM S02's with a different tire you should get a 245 rear as the OEM's have an unusually wide contact patch. Otherwise you will be adding more oversteer with the skinny rear tires.
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Although I ran non OEM rears that were 225s the first time I replaced mine (didn't know any better) and while the car was a bit tail happy I never had the kind of problems the OP is describing.

You may also want to check to see if the tires are directional. Most high performance tires are. If so, there will be an arrow on the sidewall pointing the correct direction for the tire to be mounted. Check to see that both are mounted correctly.

 

Probably air pressure, tire size difference won't cause the problems you're incurring.....

 

Your symptoms are that of different rear tire diameters. Either your pressures are significantly different or you have 2 different sized tires on the rear.

 

Assuming you got the same tire on both sides of the car, this is not what's causing your problems. Go check the pressures. Use the information stamped on the label on your door jamb to see what pressures you should be using. Differences in pressures from side to side is usually what causes your situation.

These are also NOT the correct tire size since they aren't the OEM tire for this car.

 

So to sum up, 4 out of 5 respondents suggest checking your tire pressure.

But if there's only a pound or two difference you may have other problems.

 

Thanks for your help. It was the tire pressure. left @30, right @10. Can't find a nail, but doesn't mean there isn't a hole. Thanks!