Drive Smart: The World Of Brakes & How They Work...

Comparison Between Disc Brakes and Drum Brakes

Before one can understand the benefits or disadvantages of drum brakes or disc brakes, one has to understand how they function.

Drum brakes function when the brake pedal is pressed which exerts pressure on the brake fluid. The pressure is then transmitted uniformly from the master cylinder, through a pipe, to the slave cylinders near the wheels. This will then move the slave pistons forward, forcing the brake pads against the drums attached to the wheels to slow down the vehicle.

Disc brakes function by the brake callipers applying pressure to the brake discs, thus creating friction which then slows the vehicle down to a stop. This brake system functions somewhat similarly as compared to the drum brakes. Pressure is applied to the brake pedal which then transmits a uniform pressure via the brake fluid which is transmitted from the master cylinder to the slave cylinders located near the wheels.

The Causes of Brake Failure

1. It is important to note that this system works only because of the fact that the brake fluid is incompressible, any contamination within the fluid will effect the braking efficiency of the vehicle. 
2. If an air bubble is detected within the system, the effectiveness of the system will be affected. The pressure applied in the master cylinder will not be effectively transferred to the slave cylinders as the air bubble is incompressible. This will affect the motion of the pistons in the slave cylinder and as a result the braking efficiency of the vehicle is affected.

Composite Materials in Brake Systems

On high performance and exotic vehicles, composite materials for the brake systems are offered as an option or as standard. For example the Ferrari 458 Italia offers Carbon Ceramic Brakes as standard whereas, the Porsche 911 Carrera S offers it as an option for US$8520 in the American market. 

Porsche's PCCB System
(Porsche Ceramic Composite Brakes)

The advantages of using composite materials such as ceramic or carbon are their high heat tolerance, mechanical strength and their reduction in weight as compared to standard iron discs. As an example, Porsche's PCCB system achieves a 50% weight reduction and a higher temperature tolerance with a significant reduction in generation of brake dust as compared to the standard steel discs.