Originally Posted by GregW / Oregon
I don't read that the way you do. The first most important "area" is the total piston area--A large single piston may have more area than dual pistons. This inceases potential clamping force and therfore stopping power.
"Increasing the size of the pads will not increase clamping force." The area over which the clamping force is applied is moot in terms of stopping power; larger "swept area" will only increas pad life, as each sq. cm. of pad is doing less work.
The second most improtant area is the rotor size; larger rotors offer a greater heat sink and area with which to dissapate heat.
Sure, I would agree, however, I am not so sure that the M3's large single piston has more stopping "area" than Porsche's multi-piston caliper.
Without going back and checking the rotor sizes on each car, I'd have to guess -from memory- that the rotors are very close in size.
Larger rotors do increase heat sink as does the type of material used, the method by which they are made and the ventilated efficiency.
The part about an increase in pad size only increasing pad life applies to enlarging a pad without equally enlarging the forces behind it; i.e. more pistons and/or larger ones, which would create more pressure per sq. cm.