I have an Audi TT 2002 quattro. After only 15,000 miles on a set of new tires, they have worn bald. And on each wheel, the tire has worn most on the inside. Each wheel! Is this a common problem on these cars? What is the likely repair that would be required, and how much does it cost? Would you trust anyone else (or any one BUT) an Audi dealer to do this repair?