I purchased a set (thru Tire Rack) of17x8 Mille Miglia mm2-5 spoke rims and Yoko A520 Tires for my '97 1.9 Z3. They came balanced and mounted for simple bolt on. I have had a slight shimmy in the steering wheel between 40-50mph, and when braking. The brake rotors are new, so I know thats not the reason (and there is no pulsing in the brake pedal). I have put about 2000 miles on them, and just had them re-balanced at a Goodyear center. It seems that the problem is a little WORSE now. What Gives???