Drum brakes are a type of braking system commonly used in vehicles, especially in the rear wheels. They consist of several components, including the brake drum, brake shoes, wheel cylinder, return springs, and adjusting mechanism. When the brake pedal is pressed, the brake shoes press against the inner surface of the brake drum, causing friction that slows down the rotation of the wheel.
Drum brakes work on the principle of hydraulic pressure, where brake fluid is used to transmit force from the master cylinder to the wheel cylinder, which in turn pushes the brake shoes outwards.
The purpose of this article is to provide a comprehensive overview of what are drum brakes on a car, including their components, how they work, their advantages and disadvantages, and common issues and maintenance practices. By providing this information, the article aims to help readers gain a better understanding of the importance of brakes in a car and the role that drum brakes play in the overall braking system.
Additionally, the article seeks to educate readers on how to recognize and address common brake issues and to provide tips on proper maintenance to ensure the safety and longevity of the vehicle.
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Components of Drum Brakes
Brake drum
The brake drum is a cylindrical component located behind the wheel that rotates along with the wheel. It is made of cast iron and serves as the outer surface against which the brake shoes press to slow down the wheel’s rotation.
The brake drum provides a large surface area for the brake shoes to contact, which increases the braking force and dissipates heat generated during braking. Brake drums need to be machined periodically to maintain a smooth surface and prevent vibrations, which can cause noise and reduce braking performance.
Brake shoes
The brake shoes are metal plates with a friction material lining that presses against the brake drum when the brakes are applied. Brake shoes are usually curved to match the shape of the brake drum, and they are mounted on a brake shoe anchor pin.
Brake shoes typically have a leading and a trailing shoe, with the leading shoe being the one that first makes contact with the drum. The friction material on the brake shoes needs to be periodically checked and replaced when worn out to ensure proper braking performance.
Wheel cylinder
The wheel cylinder is a hydraulic component that is mounted inside the brake drum and is responsible for pushing the brake shoes against the drum when the brakes are applied. It consists of a piston that is connected to the brake shoes via a push rod. The wheel cylinder is connected to the brake lines, which carry brake fluid from the master cylinder.
When the brake pedal is pressed, the master cylinder sends pressurized brake fluid to the wheel cylinders, which then push the brake shoes against the drum.
Return springs
Return springs are used to retract the brake shoes when the brakes are released. They are typically located on the opposite side of the brake shoes and are attached to the brake shoe anchor pin. Return springs ensure that the brake shoes do not remain in contact with the brake drum when the brakes are not applied, which reduces brake wear and drag.
Adjusting mechanism
The adjusting mechanism is used to maintain the proper clearance between the brake shoes and the brake drum as the brake shoes wear down over time. The adjusting mechanism consists of a threaded adjuster that is located between the brake shoes and is turned by a star wheel adjuster. As the brake shoes wear down, the star wheel adjuster turns the threaded adjuster, pushing the brake shoes outwards to maintain the proper clearance.
The adjusting mechanism needs to be periodically checked and adjusted to ensure that the brakes are operating correctly.
How Drum Brakes Work
When the brake pedal is pressed, hydraulic pressure is generated in the master cylinder, which is then transmitted to the wheel cylinders. The wheel cylinders then push the brake shoes against the brake drum, causing friction that slows down the rotation of the wheel.
The kinetic energy of the car is converted into heat energy through friction, which is dissipated through the brake drum and the surrounding air. When the brake pedal is released, return springs retract the brake shoes, and the wheel is free to rotate again.
Drum brakes are less efficient than disc brakes because they have a smaller surface area for friction and tend to overheat more easily. Disc brakes are more commonly used in the front wheels of a car because they provide better stopping power and dissipate heat more effectively.
Drum brakes are still widely used in the rear wheels of cars, as they are less complex and less expensive to manufacture and maintain.
Advantages of drum brakes
Drum brakes have several advantages that make them a popular choice for the rear wheels of cars. One of the main advantages of drum brakes is that they are less complex and less expensive to manufacture and maintain than disc brakes.
Drum brakes also have a larger surface area for friction than disc brakes, which can provide better stopping power in certain situations. Additionally, drum brakes are less affected by water and debris than disc brakes, which can make them more reliable in certain environments.
Disadvantages of drum brakes
Despite their advantages, drum brakes also have several disadvantages that can make them less desirable than other types of brakes. One major disadvantage of drum brakes is that they tend to overheat more easily than disc brakes, which can cause brake fade and reduce stopping power.
Drum brakes are also less effective than disc brakes at dissipating heat, which can cause them to wear out more quickly. Additionally, drum brakes can be more difficult to service and repair than disc brakes, which can lead to higher maintenance costs.
Common problems with drum brakes
Drum brakes are a crucial component of a vehicle’s safety system, and as such, they can experience several issues over time. One common problem with drum brakes is brake fade, which occurs when the brakes overheat and lose their stopping power.
Another common issue is worn brake shoes, which can cause reduced braking performance and increased stopping distances. Brake noise, uneven braking, and leaking brake fluid are also common problems with drum brakes. Regular maintenance, including inspection and replacement of worn components, can help prevent these issues from occurring.
There are several signs that can indicate problems with the drum brakes. One of the most obvious signs is a squeaking or grinding noise when the brakes are applied, which can indicate worn brake shoes or a damaged brake drum. Reduced braking performance, longer stopping distances, or a soft brake pedal can also be signs of brake problems.
If the brake warning light on the dashboard comes on, it can indicate low brake fluid or a problem with the brake system that needs to be addressed immediately.
Addressing brake issues promptly is essential to ensure the safety of the vehicle and its occupants. Neglecting brake problems can lead to reduced stopping power, longer stopping distances, and increased risk of accidents.
Additionally, ignoring brake problems can lead to more extensive damage to the brake system, which can be more costly to repair. It is recommended to have the brakes checked by a professional mechanic as soon as any signs of brake problems are detected.
The cost of drum brake repairs can vary depending on several factors, including the extent of the damage, the type of vehicle, and the location of the repair shop. Simple repairs, such as brake shoe replacement or adjustment, can cost a few hundred dollars, while more extensive repairs, such as brake drum replacement or wheel cylinder repair, can cost several hundred dollars or more.
Regular maintenance, including inspection and replacement of worn components, can help reduce the cost of brake repairs over time by preventing more extensive damage to the brake system.
Drum Brake Maintenance
Regular maintenance is essential for the proper functioning of drum brakes and to ensure the safety of the vehicle and its occupants. Regular maintenance can help prevent problems before they occur, extend the life of the brake system, and improve braking performance. Neglecting regular maintenance can lead to more extensive damage to the brake system, which can be more costly to repair and compromise the safety of the vehicle.
The recommended maintenance schedule for drum brakes varies depending on the type of vehicle and driving conditions. In general, it is recommended to have the brakes checked by a professional mechanic at least once a year or more often if the vehicle is driven in extreme conditions.
Brake fluid should be replaced every two years, and brake shoes and brake drums should be inspected at every tire rotation or every 10,000 miles. These are general recommendations, and vehicle owners should consult their owner’s manual or a professional mechanic for specific recommendations for their vehicle.
There are several DIY maintenance tips that vehicle owners can follow to help maintain their drum brakes. Regularly cleaning the brake components with brake cleaner can help remove dirt and debris that can cause brake noise and wear. Adjusting the brake shoes and parking brake can help maintain proper clearance between the shoes and drum, which can improve braking performance and reduce wear. Additionally, replacing worn brake shoes and brake drums can improve braking performance and prevent more extensive damage to the brake system.
Professional inspections are an essential part of brake maintenance and can help detect problems before they become more extensive and costly to repair. Professional inspections can include checking the brake shoes, drums, wheel cylinders, and brake lines for wear and damage.
A professional mechanic can also check the brake fluid level and quality, adjust the brake shoes and parking brake, and test the braking performance. Professional inspections should be conducted regularly, and vehicle owners should consult a professional mechanic if any signs of brake problems are detected.
Conclusion
Drum brakes are a type of braking system commonly used in vehicles, especially in the rear wheels. They consist of several components, including the brake drum, brake shoes, wheel cylinder, return springs, and adjusting mechanism. When the brake pedal is pressed, the brake shoes press against the inner surface of the brake drum, causing friction that slows down the rotation of the wheel.
Drum brakes work on the principle of hydraulic pressure, where brake fluid is used to transmit force from the master cylinder to the wheel cylinder, which in turn pushes the brake shoes outwards.
Proper maintenance is crucial for the safe and efficient operation of drum brakes. Regular maintenance, including inspection and replacement of worn components, can help prevent problems before they occur, extend the life of the brake system, and improve braking performance. Vehicle owners should follow the recommended maintenance schedule for their vehicles and have the brakes checked by a professional mechanic regularly.
Additionally, vehicle owners should be aware of signs of brake problems, such as reduced braking performance, brake noise, or warning lights, and have them addressed promptly to prevent more extensive damage to the brake system.
Drum brakes are an essential component of a vehicle’s safety system, and their proper functioning is crucial to prevent accidents and protect the occupants of the vehicle. Drum brakes have advantages and disadvantages compared to other types of brakes, and the choice of brake system depends on several factors, including the type of vehicle, the driving conditions, and personal preferences.
Regardless of the type of brake system, regular maintenance and prompt attention to signs of brake problems are essential to ensure the safety of the vehicle and its occupants. Vehicle owners should prioritize the maintenance of their brake system and seek professional help if any signs of brake problems are detected.
