I had a Mercedes (sorry) with a similar problem. The tires cupped, but everything was in alignment and within specs. After THREE sets of tires, I talked with the technician, and he agreed that while within specs, there was a problem. He made the adjustments closer to the minimum in the spec range, and the issue disappeared! Problem is that you have to wait until your tires are ruined AGAIN before you know whether or not the process worked. Good luck!