Mike, It might be that one of your rotors are out of balance. Maybe you should have your tires balanced while they are on the car. Another posibility is that your tires could be out-of-round. Jack each wheel off the ground until they spin freely. Spin each wheel and see if the distance from wheel to ground changes as the tire spins. I've heard of wheel shops that can 'true' tires, but I've never seen it done. For those of you who don't know, to 'true' a tires means to grind or wear away any high spots to make the tire round. Walt Tampa, FL WATSDAT