How Disc Brakes Work:
When the driver steps on the brake pedal, the power is amplified by the brake booster (servosystem) and changed into a hydraulic pressure (oil-pressure) by the master cylinder. The pressure reaches the brakes on the wheels via tubing filled with brake oil (brake fluid). The delivered pressure pushes the pistons on the brakes of the four wheels. The pistons in turn press the brake pads, which are friction material, against the brake rotors which rotate with the wheels. The pads clamp on the rotors from both sides and decelerate the wheels, there by slowing down and stopping the vehicle.
Basics of Disc Brakes:
Disc brakes are found on most vehicles today. They are mounted on the front axle and often
the rear as well. To stop a wheel (and your car), a disc brake uses a caliper fitted with brake
pads to grab a spinning disc, or rotor.
The caliper is an assembly mounted to the vehicle with a bracket so it frames the rotor. It looks and functions like a c-clamp. It contains:
– Brake Pads: metal plates bonded with material that provides stopping friction.
– One or two pistons to push the brake pads against the rotor when you brake.
– A bleeder screw to allow for servicing the brakes and replacing the fluid.
– A rubber piston seal that prevents brake fluid leakage and retracts the piston when the brakes release.
– A dust boot to keep contaminants out of the cylinder.
– Anti-rattle clips that keep the brake pads stable.
The Rotor is made of cast iron or a steel/cast iron composite. It’s attached to the wheel hub
and turns with the wheel. It’s the surface the brake pads contact. When you step on the brakes, pressurized brake fluid pushes against the pistons inside the caliper, forcing the brake pads against the rotor. As the brake pads press against both sides of the disc, the friction stops the wheel’s rotation.
Rotors can either be solid or vented. Vented ones have more surface area and can more easily dissipate heat.
