single piston and dual or even 4 piston brakes are not equal. The single piston caliper was cheaper to make than the 4 piston caliper, but the 4 piston caliper was superior in the fact that it gave better modulation of the braking power. Motorcycles use 6 piston calipers now. If you added up all the area of a 4 piston caliper to a single piston, you may be suprised on the difference in total area. if your running 13 brakes front and real and are applying 900 psi to both with the same piston surface area and pad area, they are going to brake equally, then the rear is gonna lock up as the car is gonna dive onto the fronts and unload the rear weight. It can be done but there will be alot of biasing done in the valve to get the rears not to lock up before the fronts. Todays pizza sized rotors are all controlled by ABS computers. Ask an exotic or huge rear brake owner how often the rear brake pads are serviced. I think huge rear rotors are just to balance the look of the exposed rotors, they probably run small piston calipers on them that look the same size outside.
