Disc brakes are on the front of nearly every modern car and on all four wheels of most. The system looks complex, but the idea is simple: it turns the push of your foot into friction that slows the wheel. Here is the whole chain, step by step.
From your foot to the wheel
- You press the pedal. The pedal pushes a piston in the master cylinder.
- Fluid carries the force. Brake fluid is nearly incompressible, so it transmits that push through the brake lines to each wheel. Learn more in our brake fluid guide.
- The caliper clamps. At the wheel, fluid pressure pushes the caliper's piston, which squeezes the brake pads against the spinning rotor. See how a caliper works.
- Friction slows the wheel. The pads grip the rotor, friction converts the car's motion into heat, and the wheel slows.
- You release. Pressure drops, the caliper lets go, and the wheel spins freely again.
The key parts
- Rotor (disc): the metal disc that spins with the wheel; the pads grip it.
- Brake pads: the friction blocks that press the rotor - the main wear item. Shop brake pads by vehicle.
- Caliper: houses the piston(s) and holds the pads.
- Hardware: clips and shims that position the pads and keep them quiet - refresh with a hardware kit.
Why heat is the enemy
Because braking makes heat, the whole system is designed to shed it - that is why rotors are often vented and why pad compounds are rated for temperature. When parts cannot shed heat, you get brake fade. For the wear items that keep this system working, keep pads and rotors in good shape and replace them on time - see when to replace pads.