Hi everyone

so today I had the s belt replaced on my new / used purchase for my car that has 93 on it. the dealer said the car is really clean all around so that was good to hear. my question is i also had my wheels balanced and the runs fine although i sense there is a vibration in the cabin but not in the wheel. when I had the wheels balanced the tech said the 19 inch tires i had sucked (federals). I also was able to pick up 18 inch rims and plan on getting these balanced that have continental extremes on them which are more performance tires. so my question is would the 19 inch rims with crap tires cause this cabin vibration? I hope to have the fix by putting the 18s back on with better tires. I also know that the 19s run rougher and also have the tendency to hit the wheel well at small bumps using these Federals which are not the lowest profile either. once again wondering if the slight vibration in the cabin would be caused by this or something else.

car is an absolute blast to driver...convertible, with red leather interior....

 

If your vibration can be felt through your seat or your clutch pedal, try swapping your front and rear tires. If your steering wheel now has the vibration you have now found that the vibration is in the wheel. Now all you have to do is isolate which one(s) is(are) the culprit(s). Most tire shops have a regular balancing machine...look for one with a road force balancer that way if there are any tread imperfections the road force will apply weights where necessary to negate the tread imperfections effect.

 

Independant to your vibration problem, I would point out that changing the wheel diameter would entrain the problem of speed indication and milage recording. A 19" wheel has a circumference of 59.69026041 inches. An 18" wheel has a circumference of 56.548667764616276. That means for 1 turn of the road wheel, the car will have travelled some 3 inches LESS. This of course pre-supposes the same tire height. Check carefully before changing wheels and tires, if you wish to keep your speed and mileage incations accurate. Incidently, my Audi S6 runs on 19" wheels with a tire height of 35mm, with which the car was manufactured. I have no vibration problems, though I have had to rebalance the wheels.

 

thanks everyone. it was the front rims were very slightly bent so the tires were rotated to the back. i will be exploring the 19 rims per your suggestion as these extra rims came with my new S4 purchased 2nd hand....i sent it to audi service and they charged be 27.00 usd so it was not bad. they also checked the driver side window since I though there was some wind noise coming in between the soft top and driver side window. they claim is was measured to factory spec. personally i think its a hair off but not sure what else i can do here. thanks again for the help!