Doomer, it's caused by sidewall flex. I had the same problem on the dunlops that came off the rear of may car. It doesn't help that the rear is the easiest to camber out also. But it was still in spec when I aligned the car. It's only happened on the dunlops though, b/c I've had Sumitomo Htr ZII's on my car for almost a year with no sign of tire wear on the inside edge of the tire. Also make sure you rotate them every 3-5000 miles.