No doubt about it- brake calipers are one of the most, or even the most, important automotive brake parts. Without a working caliper(s), you might as well just park the car - wherever you are.
The car’s wheels are attached to circular metal rotors and these rotors spin along with the wheels.
The caliper fits over the spinning rotor much like a clamp- step on the brakes and the caliper grabs the spinning rotor by applying squeezing pressure, and thus slowing the car.
Today, there are several types of calipers in use:
A floating caliper has piston(s) only on one side of the rotor which slides back and forth on bushings or pins, acting as a clamp.
When the brakes are applied, the piston pushes the brake pad only on the inboard side of the rotor.
The caliper then slides on the bushings or pins and squeezes the outboard pad against the rotor, and thus initiates braking action.
The sliding caliper type disc brake is mounted in a slot in the caliper adapter. It is a variation of the floating caliper design, using a single piston and operating on the same principle - the piston applies pressure to one brake pad and the movable caliper applies pressure to the other.
A fixed caliper usually consists of 2, 4, 6 or even 8 pistons. A fixed caliper is mounted to a bracket with no sliding pins or bushings in its mount.
The fixed caliper consists of an equal number of pistons on both the inboard and outboard halves of the caliper. It is generally accepted that fixed calipers have better performance, but at a higher cost.
Short of replacing your car’s current brake system with larger rotors, which often means new caliper and sometimes wheels, you can fine tune your present braking system to perform better:
A specialized (but releatively cheap tool) is the Brake Caliper Tool. When a pad is almost all used, it pushes back the piston so that new brake pads can be easily removed and replaced.