What are Brake Calipers?
Brake calipers hold the brake pads. They are hydraulic actuators that transfer force from application of the brake pedal to the friction material (brake pads) via hydraulic fluid contained in lines that interconnect the brake pedal assembly and the calipers. Calipers may be used on the front or rear brakes and are mounted to the spindle assembly over the brake rotors.
There are two main types of calipers: floating calipers that move in and out relative to the rotor and have one or two pistons only on the inboard side of the rotor, and fixed calipers that don’t move but have pistons arranged on opposing sides of the rotor.
How do Brake Calipers Work?
The transfer of energy begins with operation of the brake pedal, which transfers motion to the brake master cylinder. Pedal motion causes a piston in the master cylinder to push hydraulic fluid out into the brake lines. The pressurized fluid is directed to the calipers and/or wheel cylinders at all four road wheels. Pressurized brake fluid enters the caliper, filling the chamber behind the caliper piston and forcing the piston outward. As pressurized brake fluid forces the caliper piston outward, it pushes the friction material into contact with the brake rotor. The brake caliper applies braking pressure to the friction material proportionate to the applied force from the vehicle operator. Upon completion of the braking action, the brake pedal is released, brake fluid pressure reduced, and the caliper piston and friction material are retracted away from the brake disk.
How are Brake Calipers Made?
The caliper is traditionally cast of lightweight aluminum material. Older brake caliper designs may be cast iron. FA brake caliper can operate using 1, 2, 4 or even 6 pistons. Single piston designs are designed to allow the caliper to center during application so that the inboard friction material has an equally applied force with that of the piston side. Dual, 4 or 6 piston calipers apply hydraulic force from both sides of the caliper.
Why do Brake Calipers Fail?
- Internal rust and corrosion
- Seized caliper guide pins
- Broken bleeder screws
What are Symptoms of Brake Caliper Failure?
- Asymmetric brake pad wear
- Dissimilar pad wear on either the passenger or driver side
- Steering pull
- Brake pads soaked with dark colored fluid and an accompanying odor
What are the Consequences of Brake Caliper Failure?
- Reduced braking effectiveness
- Increased stopping distance