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.
Fixed opposed piston calipers
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.
High performance brakes
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:
- Bigger Pistons: Bigger pistons have greater clamping area and thus more clamping force over the rotor
- More Pistons: High performance calipers that allow for more pistons- six-pistons and even 12-piston models can increase the clamping force of the caliper.
- Less Heat Retention: Brake air scoops can help in this area; larger rotors can spread excess heat over a larger area
- Differential bore Calipers: It helps if the pistons closer to the rear edge of the caliper are larger. Differential-bore calipers use smaller pistons up front, larger pistons toward the back.
- Carbon Ceramic Brakes Rotors: These are the ultimate in brakes. They are made from siliconized carbon fiber, with very high temperature capability, a 50% weight reduction over iron discs, a significant reduction in dust, and enhanced durability in corrosive environments over conventional iron discs. The calipers are painted yellow and the discs are internally vented similar to cast-iron ones, and cross-drilled.
Brake caliper tool
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.