This entry was posted on Dec 14, 2018 by Brake Time USA
Drum brakes are the older kind beside disc brakes. They operate based on the frictional force generated between the brake pads and the interior of the brake drum, which is what stops the wheel spinning. Drum brake systems include brake shoes, which is one component that disc brakes do not have.
Components of the Drum Brake System
• Brake Pads: A pair of pads lined with a material possessing high frictional coefficient. These pads each have a single hinge or multiple close ones. The end of a pad without the lining stays in contact with the wheel cylinder pistons.
• Wheel Drum: This drum is made of cast iron, and rotates alongside the wheel.
• Wheel Cylinder: This cylinder carries two pistons for each brake pad. When the driver presses the pedal, it raises oil pressure acting on these pistons, which in turn cause the brake pads to press on the drum.
• Brake Return Springs: These springs allow the brake pads to revert to original positions after the pedal is released.
• Emergency Brake System: This works through a lever, which can be activated using a handbrake.
• Self-Adjusting System: This automatically re-adjusts the distance it takes for the brake pads to touch the drum. Since the pads wear with time, this distance needs to be adjusted every now and then. This is also the reason why drum brakes are known as self-actuating brakes.
How Drum Brakes Work
• When the driver presses the brake pedal, pressure from the master cylinder acts on the hydraulic oil, which in turn transfers it onto the wheel cylinder.
• The double-acting pistons use this pressure to push the pads outwards. The brake pads start pressing against the wheel drum's interior, and this causes friction.
• The friction between pads and drum cause the wheels to stop spinning.
• After the driver releases the brake pedals, the brake pads are brought back into position by the return springs.
• The self-actuating mechanism, as described above, involves adjustment of the distance traveled by brake pads to reach the wheel drum. Automatic re-positioning makes use of the hinges attached to the brake pads; manipulating this allows placing the pads close to the drum.
Drum brakes are still preferred by many car owners due to their classic car quality. They also last longer because of the higher friction contact area.