A hydraulic brake system is one that uses brake fluid to transfer pressure to the wheels. In this system, when the brake pedal is pressed, force is exerted on the push rod, which in turn pressurizes the brake fluid, which pushes the pads against the rotor disc to stop the vehicle. A hydraulic braking system has the following parts.
- Master cylinder
This consists of a cylinder filled with brake fluid, a brake fluid reservoir, one or two pistons, ports from the main cylinder to the brake fluid reservoir and a return spring. The master cylinder receives pressure from the brake lever and conveys it to the hydraulic lines that start from it.
- Wheel cylinder
Similar to the master cylinder, the wheel cylinder receives pressure from the brake fluid and pushes the brake caliper pistons against the disc.
- Brake fluid (or brake oil) pipelines
These pipelines carry the brake fluid and connect the master cylinder to the wheels cylinder in each wheel.
- Caliper assembly
The caliper assembly contains the brake caliper pistons and the rotor disc. The caliper assembly is the component which is actually involved in the process of slowing down the wheel.
Working
When the brake pedal is pressed, the push rod presses the master cylinder’s piston. The piston pressurizes the brake fluid in the cylinder. The fluid moves through the pipelines and reaches the caliper assembly. At the caliper assembly, there are two pistons one on each side of the rotor disc and they are connected to the brake fluid. The brake fluid pressurizes each of the pistons from both the sides, and pushes them towards the rotor disc. Since there is a one way movement of the brake fluid due to the pressure from the brake lever, it is displaced in the brake fluid reservoir. This process leads to a frictional motion between the brake calipers and the rotor disc, and thus braking happens. And when the brake lever is released, the return spring in the master cylinder pushes the master piston to its original position and the displaced brake fluid returns back to the pipelines.
Brake fade
Brake fading is a common disadvantage of the hydraulic braking system. It is caused due to the following reasons:
- When hydraulic brakes are subjected to heavy work like descending down a steep inclination, they produce a lot of heat. This might, in extreme conditions, vaporize the braking fluid. This causes ineffective or weak pressure in the caliper assembly and thus faded braking.
- Due to continuous usage, the pads which cause friction over the rotor disc may become soft due to wearing. This also causes ineffective braking. It thus becomes important to check the brake pads regularly, and if necessary, replace it.