Brake calipers are one of the essential components of the disc braking system, which is the most common type of braking system found in cars today. Part of the disc brake, the caliper is a unit that contains pistons and brake pads. This assembly works to slow a car's wheels by creating friction with the rotors. Brake calipers come in two basic varieties — floating or fixed — and can be enhanced for additional braking power.
A disc braking system is made up of a master cylinder, a series of tubes and hoses, and the actual disc brake, which includes a rotor, brake calipers with attached pistons, caliper support, and brake pads. The rotor is attached to the vehicle's wheel, and the brake calipers fit over the rotors like clamps. Inside each caliper is a pair of brake pads, which are like metal shoes lined with some kind of friction material. When the brake pedal is pressed, the master cylinder forces brake fluid into the caliper, which presses against the pistons. The pistons push the brake pads against the rotor, creating the friction that causes the wheel to slow down or stop.
There are two common types of brake calipers. A floating caliper, also called a sliding caliper, moves in a track within its support and has pistons on the inboard side of the rotor only. Hydraulic pressure forces the pistons against the inner pad, which in turn pulls the caliper against the outer pad, creating friction on both sides of the rotor. A fixed caliper is mounted to the caliper support and doesn't move, using pistons on each side to press the brake pads against the rotor. Floating calipers are more common because they are less expensive to make and to service, but fixed calipers are valued for their smoothness and efficiency, and are often found on luxury vehicles.
In some circumstances, brake calipers can be customized to suit specific needs. Motorcycles with disc braking systems require small, lightweight calipers which are often made from aluminum and include multiple pistons for added clamping force. Large trucks and SUVs used for towing or cargo can be outfitted with aftermarket calipers, which provide extra braking power and a customized appearance. Additional options include performance brake calipers, which may have bigger pistons or retain less heat, and differential-bore calipers, which use a combination of small and large pistons for a more balanced and efficient braking effect.