Brake drums, pads, and rotors are an essential part of any car, in that they slow down the vehicle using friction when you hit the brake pedal. Every car’s brakes operate using either of two main friction mechanisms, each different from the other. If you did not know them, or how they differ, the following is a detailed look. Abrasive Friction This mechanism converts the energy of motion into thermal energy. It is much easier to understand if you imagine the brake pads as a pair of hands. When you rub the latter together, you get resistance, which causes some of the skin cells to break off. In much the same way, abrasive friction in brakes causes brake dust to form. European vehicles principally use this to achieve high braking performance, although this also means the brake pad and rotor would wear off much more quickly, and you would have a lot of dust to deal with as time passes. Additionally, in most cases, the rotor would be made of softer material than the pads, which are constructed out of a specific semi-metallic compound, making them prone to faster wear. Adherent Friction This mechanism transfers a slight layer from the material of the brake pad onto the surface of the rotor. The layer quickly forms a bond with the new surface and stays on as a sticky substance while the brake rotors move through the gap left by the brake pads. Adherent friction makes use of the physical properties of this transfer layer and the brake pad, which fluctuate as a result of temperature changes. The brake pad wears off just enough to form an even transfer layer on the rotor, and during each rotation, the transfer layer protects the rotor from wear, while also absorbing energy. Considering the way this works, it is a no-brainer for people who put their cars to everyday street use. The downside though, is that adherent friction becomes less effective when higher temperatures enter the equation. For that reason, this braking mechanism is not suited to cars intended for high performance, but are rather seen in vehicles of Asian and domestic manufacture. The brake pads used for this usually constitute a ceramic formula, while the rotor is made out of hard cast iron. The best thing about using an adherent friction mechanism is that you lose very little material each time you use the brakes.