What's the most important part of an automobile's braking system? Granted, every component in this area is vital, from pedal to rotor as well as the lines, hoses, hydraulic fluid, boosters, proportioning valves, antilock systems, and calipers in between. If any piece malfunctions, the entire system is adversely affected, and stopping is no longer a given. But assuming that everything is working properly, we ask again, what part of a braking system is most important? We submit that the lowly brake pad is right up at the top of the list. Braking, as you know, is a matter of friction--to paraphrase our overview piece, a vehicle's forward momentum is counteracted by the frictional forces created when its brake pads are clamped down onto a brake rotor. Where the pad meets the rotor is where braking happens, and installing high-performance brake pads can make for quicker, more consistent stops.
The stresses at this flash point are enormous, and brake pad >> engineers have a lot of variables to balance. Friction generates heat, which is a necessary by-product of brake action, but also the number one enemy of good and consistent braking. The more friction during braking the better the stopping, but how a pad handles the resultant heat is critical to brake system performance. Gas is also created, and must be evacuated, as the resin that holds the brake pad material together is broken down. There's also the problem of shear forces, as the spinning rotor attempts to rip the pad material from its backing plate. We don't need to explain why that would be bad. Then, in a street-driven car at least, there are the issues of brake noise and pad and rotor wear.
Disc brake pads, for the most part, are compromises. With a common OEM-style pad, friction, and therefore stopping power, is compromised in favor of low noise, low wear, and low dust levels. Competition pads are compromised in the other direction; noise and dust are irrelevant, and the pads only have to last as long as the race does. In this age, though, the level of innovation, technology, and engineering put into high-performance street-going brake pads means that super stopping power comes with acceptable levels of noise, dusting, and wear.
"Installing a set of high-performance brake pads," says Jerry DeMarino of Hawk Performance, "is the single biggest improvement someone can make to their car's brake system." This is even more so, according to DeMarino, if said car is wearing sticky, larger-than-stock tires, since the extra "stick" creates more heat in the brake system.