In a disc brake system, the hydraulic pressure is converted into a clamping force. As the hydraulic fluid (brake fluid) is pressurized by the master cylinder, the pressure is dissipated by moving another cylinder. These are called wheel cylinders. The wheel cylinders are located in calipers. Calipers are rigid units attached to the suspension of the car that contain the brake pads and wheel cylinders. These are u-shaped so that they can straddle the rotors. When the wheel cylinder is compressed, the compresses the springs that hold the brake pads away from the rotor (the rotor is a solid disk of metal). The two brake pads then contact the rotor on both sides forming a sort of braking sandwich (pad rotor pad). As the pads contact the rotor, friction is developed that slows the rotor and the wheel attached. This action is similar to spinning a bicycle wheel and then stopping it by clamping two opposing fingers to the rim surface.

Most brake systems are self adjusting for pad or shoe wear. This is accomplished automatically as the car is driven in reverse. The mechanisms compensate for the worn pads or shoes by sensing the contact point and moving slightly outwards.