The brake system is one of the most important safety features on your vehicle, one in which you trust with not only your own safety, but the safety of your family. Modern automotive braking systems rely on hydraulic fluid to translate the force the driver applies to the brake pedal into stopping power at each of the four wheels.
Master Cylinder
The master cylinder is the heart of your vehicle's brake system. It takes the input force the driver applies to the brake pedal and channels that force through hydraulic lines to the four wheels. Most modern master cylinders incorporate a dual reservoir design. This means that there is a separate hydraulic circuit for the front and rear brakes. If one of the brake lines should be damaged or cut. The brakes on the other circuit will continue to function.
Power Booster
The power booster is usually mounted in the engine bay between the master cylinder and the vehicle's firewall. Its job is to amplify the force the driver applies to the brake pedal. This not only lessens the amount of force needed by the driver to engage the brakes, but also lessens the distance the brake pedal needs to travel. Most automotive power brake boosters are powered by vacuum generated by the engine.
Brake Rotor
A brake rotor is a thick steel or aluminum disc that attaches to the wheel hub just behind the wheel. It works in conjunction with the brake caliper to slow the vehicle down when the brake pedal is applied. As a general rule the larger the brake disc the shorter the distance a vehicle will need to come to a complete stop from a given speed. Brake rotors have a tendency to become extremely hot during use, so some manufactures incorporate cooling slots or holes to improve brake performance
Caliper
The brake caliper is mounted over the brake rotor and is the muscle of the disc brake system. It is usually a cast iron or aluminum piece with a piston inside. Brake fluid travels from the master cylinder and forces the piston out of its bore, which in turn pushes the brake pad against the brake rotor and slows down the vehicle. High performance vehicles such as sports cars usually incorporate a four wheel disc brake setup.
Brake Drum
Drum brakes are an older technology, which is still used on the rear axles of many cars and trucks manufactured today. A large drum or bowl rides on the wheel hub and rotates with the wheel. When the brake pedal is applied the brake shoes are pushed against the inside of the brake drum slowing the vehicle down. Brake drums are no longer used on the front axles of vehicles, because they offer much less stopping power than disc brake systems.
Wheel Cylinder
The wheel cylinder does for drum brake systems what the brake caliper does for disc brake systems. It is mounted to the drum backing plate behind the brake drum, and is a small round cylinder with plungers on each side. When force is applied to the brake pedal, brake fluid travels from the master cylinder to the wheel cylinder. This causes the plungers to extend and in turn these plungers force the brake shoes against the brake drum.
Brake Pad/Shoe
The terms brake shoes and brake pads are sometimes used interchangeably but in technical terms brake shoes refer to the linings in a drum brake system and brake pads refer to the linings in a disc brake system. They are both comprised of a friction surface mounted on a steel backing plate, and must be replaced periodically, whenever the friction surface wears below tolerable safety levels.
