Originally Posted by GregW / Oregon
Brake System Basic Facts
1) Line pressure can only be increased by either increasing the mechanical pedal ratio or by decreasing the master cylinder diameter. In either case the pedal travel will be increased.
2) Clamping force can only be increased either by increasing the line pressure or by increasing the diameter of the caliper piston(s). Increasing the size of the pads will not increase clamping force. Any increase in caliper piston area alone will be accompanied by an increase in pedal travel. The effectiveness of a caliper is also affected by the stiffness of the caliper body and its mountings. It is therefore possible to reduce piston size while increasing caliper stiffness and realize a net increase in clamping force applied. This would typically improve pedal feel.
3) Only increasing the effective radius of the disc, the caliper piston area, the line pressure, or the coefficient of friction can increase brake torque. Increasing the pad area will decrease pad wear and improve the fade characteristics of the pads but it will not increase the brake torque.
It is true that multiple piston calipers do not necessarily offer more clamping force than single pistons, but might offer more piston area making this possible.
Swamp, obviously, the previous post regarding the color of the brakes was directed at Porsche, so I have to chime in. Feel free to lambaste me at will. I am accustomed to it. However, facts are facts.
+1 to the aforementioned post. More force over more of a swept area, making multi-piston brakes more effective than single piston ones. Everything else being equal, of course.
So, whether the rigid four and six piston "red" brakes on a Porsche offer "more" clamping force is moot. It is that they offer more clamping force over a broader area. Which is why BMW's brakes -in their current configuation- will not compete with Posche's over repeated hot stops. No matter how much road test data someone finds where the M3 bests the 911 in a single contest.
Whether or not better brakes are needed for the street has yet to be determined, however.
Great info, by the way!