I had the same problem and worked it gradually which cost me a replacement set of tires because I took too long to do it. But as TCD says, the Thrust Arm Bushings are a potential cause. I had the entire front end redone at 178K for the cost of 1K. A month later new rotors and pads all way around. Front struts this past Friday. Braking shimmy is gone now, but the delayed front end maintenance on the Thrust, Control and rest of that wiped out my tires. So Weds they come in. My advice is to have it looked at by a BMW certified type so you do not have to replace tires due to weird wear patterns. A great site for this is: