I work for Goodyear and everyone is somewhat correct as to the “cupping”. Some tread designs are more prone to chop, especially the ones with big open tread blocks on the sholders. Lack of rotation and a camber shift in your alignment on corners causes most of the problems. Taking clover leaf ramps with a 4×4 at higher speeds causes the camber to go way positive and causes the tire to dribble around the corner. Rotating tires to the rear doesn’t correct or even out tire wear, it’s just less annoying in the rear. If when driving down the road you look at the vehicle ahead of you and the tires are dribbling, very rapid up and down movement, that is a cupped tire. The cupped tire will never get better because instead of being round it has multiple edges which magnify the dribble. Throw them away and start over, rotate ever other oil change and have the alignment checked.