I've just had two Avon tyres fitted to the rear of my BMW 330ci. The first time I drove on a motorway in excess of 60mph I experienced a terrible vibration coming from the rear of the car. I went back to the tyre fitters, and they rebalanced the wheels, telling me one of the wheels had a bad imbalance.

They had to fit 10 x 10g weights plus 11 x 5g weights just in one spot stacked 3 high, as well as 3 x 10g and 3 x 5g alongside as well as 55g weights on other parts of the wheel giving a total of 255 grams of weights.

I never experienced any problems with the previous tyres, could it be that the tyre is seriously out of balance and that is the problem. I've never seen so many weights fitted to one wheel it looks ridiculous.