Brakes: Braking Systems: Braking fundamentals
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Topic IntroductionHelp

Principles of braking

Summary
Friction between braking surfaces converts kinetic energy into heat. In drum brakes, wheel cylinders force brake linings against the inside of the drum. In disc brakes, pads are forced against a brake disc.
Principles of braking

Several factors can influence vehicle braking:

An effective braking system takes all these factors into account.

A basic hydraulic braking system has 2 main sections -

There is a brake for:

Some systems have all drum brakes. Some have disc brakes on the front wheels and drum brakes on the rear, others have all disc brakes.

A basic braking system has a:

The driver pushes the brake pedal; it applies mechanical force to the piston in the master cylinder. The piston applies hydraulic pressure to the fluid in the cylinder, the lines transfer the pressure – which is undiminished in all directions within the confines of the brake lines – to the wheel cylinders, and the wheel cylinders at the wheel assemblies apply the brakes.

Force is transmitted through the fluid. For cylinders the same size, the force transmitted from one is the same value as the force applied to the other. By using cylinders of different sizes, forces can be increased or reduced.

In an actual braking system, the master cylinder is smaller than the wheel cylinders, so the force at all of the wheel cylinders is increased.

When brakes are applied to a moving vehicle, they absorb the vehicle’s kinetic energy. Friction between the braking surfaces converts this energy into heat.

In drum brakes, the wheel cylinders force brake linings against the inside of the brake drum. In disc brakes, pads are forced against a brake disc. In both systems, heat spreads into other parts and the atmosphere, so brake linings and drums, pads and discs must withstand high temperatures and high pressures.

On modern vehicles this basic system has some refinements, such as a power booster. This helps the driver apply the brakes.