I just bough my car, and i noticed that the car has two different sets of tires on it. The front has pirelli tires on it, and the back has another company with a different tread. Is this bad for the quattro system or should it be fine??

 

It should be ok as long as its same size, tread etc.otherwise it might affect your mileage.

 

John,

According to my owners manual, in order not to damage the Quattro system Audi recommends that all the tires have the same tread pattern and be of the same size. So if the tires have a different tread, as you have said in your post, you need to replace at least two of the tires.