I have experience with changing rotor sizes a few times, and caliper piston sizes twice. The bigger rotors going from 11" 2nd gen Explorers, to the 12"(01 Sport Trac) isn't much you feel in power or brake balance. It's minor so most people won't notice it. That's what this thread is about, moving from a 12" 3rd/4th gen rotor to the Aviator 13" rotor. I rely on the other's posts for the accuracy of swapping those parts. The piston size is critical to brake power, and balance. I first went from 2nd gen brakes to my custom parts, over 1.5" bigger rotor, but the caliper pistons were about 1/8" larger each. That would lock the brakes at any speed, without ABS. My ABS didn't like it at 80mph. That power gain was the calipers, not the rotors. I later changed to a smaller caliper(piston size). The almost stock piston area resulted in a great balance, near normal but with still better than stock power. The bigger rotors are better, no doubt, but slight changes of caliper size(piston area) make big changes to the power and balance. I'm going to a bigger caliper again to gain pad size(volume), and I think it will require a "smaller" master cylinder. I'm planning to try a Ranger MC to slightly lower the fluid pressure with the bigger calipers.