The caliper disc brake is a device for stopping or slowing the spinning of a wheel. To be able to do this, friction is applied in the form of brake pads. These brake pads are mounted in a brake caliper. Friction can be applied hydraulically, electromagnetically, pneumatically or mechanically to both sides of the disc. As its name suggests, this brake has two important parts: the caliper and the disc.
The Disc
The disc or rotor is typically made of ceramic or cast iron. Its design varies. Some are cored out with fins which join together the two contact surfaces of the disc. Hollow discs allow generated heat yo dissipate. Some have holes drilled through them. These discs are usually used in many higher performance brakes. These holes provide the gas a place to escape. Some discs are slotted to aid in removing gas and dust. Racing enthusiasts usually prefer slotted discs to remove water, gas and de-glaze brake pads. This type of disc is usually not used on standard vehicles because they easily wear down. Some are both slotted and drilled. Discs are usually damaged in scarring, cracking or warping. If you think your disc is damaged, it is more advisable to replace it altogether than to repair it. It is usually cheaper that way.
The Caliper
The brake caliper is the part which houses the pistons and brake pads. These pistons are typically made of chrome-plated iron or aluminum. There are two kinds of calipers: fixed and floating. A floating caliper moves relative to the disc. It moves along a line which is parallel to the disc’s rotation axis. It uses a piston on one side of the disc which pushes the brake pad. It then makes contact with the braking surface causing the wheel to stop spinning. A fixed caliper does not move with respect to the disc. It uses at least one pair of pistons that clamp on each side of the disc. It is more expensive and more complex than a floating caliper.