Drum brakes have been used in automobiles for nearly a century, but due to its reliability and powerful braking force, drum brakes are still installed on many models (mostly used on the rear wheels).
How the drum brake works:
Simply put, the drum brake is a brake device that uses the stationary brake pads in the brake drum to rub the brake drum that rotates with the wheel to generate friction to reduce the rotation speed of the wheel.
When the brake pedal is stepped on, the force of the foot causes the piston in the brake master cylinder to push the brake fluid forward and generate pressure in the oil circuit. The pressure is transmitted to the brake wheel cylinder piston of each wheel through the brake fluid, and the brake wheel cylinder piston pushes the brake pads outward, causing the brake pads to rub against the inner surface of the brake drum, and generate enough friction to reduce the wheel speed. In order to achieve the purpose of braking.
Advantages of drum brakes:
1. It has the function of automatic braking, so that the brake system can use lower oil pressure, or use a brake drum with a much smaller diameter than the brake disc.
2. The hand brake mechanism is easy to install. Some models with disc brakes on the rear wheels will install a drum brake hand brake mechanism in the center of the brake disc.
3. The processing and composition of the parts are relatively simple, and the manufacturing cost is relatively low.
Disadvantages of drum brakes:
1. The diameter of the brake drum of the drum brake will increase after being heated, which will increase the stroke of stepping on the brake pedal, and the brake response is likely to be less than expected.
2. The brake system reacts slowly, and the pedaling force of the brake is not easy to control, which is not conducive to high-frequency braking actions.
3. There are many parts with complex structures, and the brake clearance must be adjusted, which makes maintenance difficult.
Working of drum brakes（Video credit: Amrie Muchta）