Our cars are VERY sensitive to tire balance, so you might want to check that if you haven't done so already. Nobody could balance my tires quite right, so I went to a local tire shop and had them do the "Ride Match" balance, which cost around $25 per tire. Each tire shop may have a different name for this type of balance, but it must be done on a Hunter GSP9700 balancing machine. Basically, it incorporates extra rollers that measure the roundness of the wheel and tire, therefore more accurately balancing the wheel/tire. Unfortunately, my shimmy @ 45-50mph is back ever since I rotated the tires. Time to go back to America's Tire Company! Raj '85 535i (240k)