of ur new wheel & tire is greater then the factory spec? i know that ur speedo and tach will be off but other then that, does it effect any other performance or function of the car?

 

It effectively changes your final drive ratio. A taller tire/wheel combo will cause a higher gear ratio (lower numerically). This can cause the cause to feel more sluggish off the line but consequently turn less RPM down the highway. Of course the inverse is true for a shorter tire.

 

The general rule of thumb is to stay within 5% of factory diameter. At least that's what TireRack told me when I bought my rims.

 

It also throws off your odometer. Try to stay within 3/4 of the diameter.

 

From first hand experience with my rims, I can say that the acceleration is slower and the speedometer will be off by an averave of 2-3 mph.