THE COMPONENTS OF DISC BRAKES
Master cylinder: The master cylinder is nothing more than a simple pump that
forces brake fluid through the braking system to energize the various parts of the
system to stop your car. The master cylinder is mechanically connected to the
brake pedal through a system of steel rods called linkage. These rods operate at
different angles using bushings that are typically made of nylon, rubber, or
Teflon. When you step on the brake pedal, the linkage pushes on a steel rod that
pushes into the back of the master cylinder. This creates the pumping action
required to actuate the braking system.
Power brake booster: Located directly behind the master cylinder and bolted
to it, the power brake booster provides power-assist during the braking process.
When you press on the brake pedal, it only requires a light touch because of the
additional power provided by this unit. Its name says it all; it boosts the braking
power. Power assist units are usually vacuum-operated devices that pull vacuum
directly from the engine. Some heavy-duty and custom vehicles use a hydraulic-
assist system known as hydra-boost, which uses hydraulic pressure from the
power steering pump to boost power when applying the brake pedal.
Typical hydra-boost system: Notice that the large vacuum canister behind
the master cylinder is gone and a small hydraulic fluid block has replaced it.
Power steering fluid under pressure is pumped to this fluid block, and when the
brake is applied, hydraulic power-assist is applied to the master cylinder, thus
reducing the amount of pedal pressure required to apply the brakes.