My 06 z4 3.0si is a sweet ride. I've had it about a year and put about 7k miles on it. the problem is that I've went through two sets of tires in that time! I get a strange rolling over of the tread edges... and the tires in general just look eaten up? I've had it aligned at the dealer twice? But tires still go bad... leaving me with terrible braking vibration and bad handling, especially after autocross or de. Any thoughts as to what my culrpit might be? Tks!