Brake Calipers

There are floating and fixed callipers. The floating piston consist of one piston and the fixed calliper only has two pistons. 

Brake callipers hold the brake pads and force them against the brake rotors when you push on the brake pedal. The callipers move in and out on slide pins, which must remain free of corrosion, excessive brake dust and road dirt. Dirty or not lubricated calliper slide pins are the biggest cause of sticking brake callipers. When performing brake pad replacement, always make sure you take care of the calliper slide pins in order to avoid a sticking brake calliper.

The disc brake calliper assembly is bolted to the vehicle axle housing or suspension.

There are 2 main types:

FIXED AND SLIDING

Fixed callipers can have 2, 3, or 4 pistons. 2-piston callipers have one piston on each side of the disc. Each piston has its own disc pad.

When the brakes are applied, hydraulic pressure forces both pistons inwards, causing the pads to come in contact with the rotating disc.

The sliding or floating calliper has 2 pads but only 1 piston. The calliper is mounted on pins or bushes that let it move from side to side.

When the brakes are applied, hydraulic pressure forces the piston inwards. This pushes the pad against the disc. The calliper is free to move on slides, so there is a clamping effect between the inner and outer pads. Equal force is then applied to both pads which clamp against the disc.