I've got an 02 xr 80 and an 03 xr 100 for the kids. I've put new EBC standard shoes on the front and rear of both bikes. The front brakes are fine but the rear brakes skreech and squeal. I've tried sanding the drums but it hasn't helped. They only seem to be noisy when covering the brakes or during light braking. They work ok but what an annoying noise. Any ideas?