Drum brake

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1963½ Ford Falcon Sprint Front Drum 02

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W800 drum brake

Tipologia tamburo

backplate

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Wheel cylinder

Drum brake is a type of brake used in automobiles and other vehicles. It works on the basic principle of friction, where brake shoes press against a spinning surface called a drum. The friction generated between the drum and the brake shoes slows down the vehicle. Drum brakes were once the dominant form of braking system for vehicles but have been largely replaced by disc brakes in many applications due to their superior cooling and stopping capabilities. However, drum brakes are still commonly used in many modern vehicles, particularly on the rear wheels, due to their cost-effectiveness and efficiency in parking brake applications.

Components

The main components of a drum brake system include the brake drum, brake shoes, wheel cylinder, brake springs, and the brake adjuster. The brake drum is a cylindrical drum that rotates with the wheel. The brake shoes are curved metal plates with friction material on one side; they sit inside the drum. The wheel cylinder contains pistons that push the brake shoes against the drum when the brake pedal is pressed. Brake springs return the shoes to their original position when the brakes are released. The brake adjuster ensures the gap between the brake shoes and drum is correct, compensating for wear.

Operation

When the driver applies the brake pedal, hydraulic pressure from the brake fluid pushes the pistons in the wheel cylinder outward. This, in turn, forces the brake shoes to expand and press against the inner surface of the rotating brake drum. The contact between the brake shoes and drum generates friction, converting the kinetic energy of the vehicle into heat and slowing down the vehicle. Once the brake pedal is released, the springs pull the brake shoes back to their resting position, allowing the drum to rotate freely.

Advantages and Disadvantages

Drum brakes have several advantages, including lower cost, simpler design, and the ability to integrate a parking brake more easily than with disc brakes. They also perform well in wet conditions since the drum covers the braking components, protecting them from water and debris.

However, drum brakes also have disadvantages. They are less effective at dissipating heat compared to disc brakes, which can lead to a decrease in braking performance under heavy use, a phenomenon known as brake fade. Drum brakes are also more complex and time-consuming to service due to the number of components involved.

Maintenance

Regular maintenance of drum brakes is essential for safe operation. This includes checking the brake shoes for wear, inspecting the drum for damage, and replacing the brake fluid as recommended by the vehicle manufacturer. Adjusting the brakes may also be necessary to compensate for wear and ensure that the shoes are correctly positioned relative to the drum.

Conclusion

While drum brakes may not be as prevalent as they once were, they remain an important part of modern vehicle braking systems, especially for rear wheel applications and in cost-sensitive markets. Understanding the components and operation of drum brakes is crucial for proper maintenance and ensuring the safety and reliability of vehicles equipped with this type of brake system.