Several factors can influence vehicle braking:
- Road surface,
- Road conditions,
- Weight of the vehicle,
- Load on the wheel during stopping,
- Different maneuvers, and
- The tires on the vehicle.
An effective braking system takes all these factors into account.
A basic hydraulic braking system has 2 main sections -
- the brake assemblies at the wheels, and
- the hydraulic system that applies them.
There is a brake for:
- when the vehicle is in motion (usually a foot brake) for retarding the vehicle motion or stopping the vehicle,
- a park brake for when it’s stationary (usually operated by hand but in some incidences are foot actuated, that is apply/release)to provide a parking phase.
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:
- brake pedal,
- master cylinder to provide hydraulic pressure,
- brake lines and hoses to connect the master cylinder to the brake assemblies,
- fluid to transmit force from the master cylinder to the wheel cylinders of the brake assemblies; and
- brake assemblies (drum or disc) that stop the wheels.
The driver pushes the brake pedal; it applies force (mechanical) to the piston in the master cylinder. The piston applies pressure (hydraulic)to the fluid in the cylinder, the lines transfer the pressure (undimmished 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.
