The brake caliper plays a central role in a disc-brake system and has two functions. First, it acts either as a bracket to support the brake pads on either side of the rotor or to support the caliper bracket itself — there are other designs, but these are the two most common. Second, it uses pistons to convert pressure exerted on the brake fluid by the master cylinder into friction on the rotor.

In simple terms, a brake caliper’s purpose is to squeeze the brake pads against the rotor to stop the car. There are two main types of calipers, a single piston and a dual piston. Most front calipers are dual piston but many cars use single piston calipers on the rear, where less braking force is needed.

Stepping on the brake pedal forces the master cylinder piston forward, compressing the brake fluid. The brake fluid forces the caliper pistons toward the rotors, pinching the rotors in between the brake pads, which creates friction and slows the vehicle.