How Do Drum Brakes Self Adjust

Ever wondered how rear drums brakes manage to adjust themselves? It’s a fascinating mechanism that ensures optimal brake performance without manual intervention. This self-adjustment feature is made possible by the master cylinder and the wheel cylinder piston.

Drum brakes rely on an ingenious adjuster mechanism that automatically adjusts the rear drums and wheel cylinder piston to compensate for wear over time. This self-adjusting feature eliminates the need for frequent manual adjustments, saving both time and effort. By understanding how drum brakes self-adjust, you can ensure your vehicle’s braking system, including the master cylinder, remains in top-notch condition.

Proper brake adjustment, including the rear drums and adjuster wheel, is vital for maintaining safety on the road. When drum brakes wear down due to regular usage, they gradually lose their effectiveness. This compromises stopping power and increases the risk of accidents. Therefore, comprehending the mechanism behind drum brake self-adjustment, including the master cylinder and wheel cylinder piston, becomes essential in ensuring reliable braking performance.

In the following sections, we will explore the intricacies of the adjuster mechanism for rear brakes and discuss its significance in keeping your vehicle’s emergency brake and rear drum brakes functioning optimally. The adjuster mechanism plays a crucial role in maintaining the proper operation of the wheel cylinder and ensuring effective braking performance.

Let’s dive right in!

How do drum brakes self-adjust?

Principle behind drum brake self-adjustment

Drum brakes self adjust by using a mechanism that advances the brake shoes closer to the drum when there is a gap between them. This mechanism is activated when you apply the brakes while driving in reverse or when you use the parking brake. The self adjuster keeps the brake shoes at the optimal distance from the drum for effective braking.

Factors contributing to automatic adjustment

Drum brakes rely on a combination of mechanical forces and friction material wear to achieve self-adjustment. There are two primary factors that contribute to automatic adjustment: the wheel cylinder and the notched wheel. These components work together to adjust the rear drum brakes, ensuring optimal performance. The wheel cylinder applies hydraulic pressure to the secondary shoe, which then presses against the notched wheel, causing it to rotate and adjust the brake shoes. This self-adjustment mechanism helps maintain proper brake shoe clearance and ensures consistent braking efficiency.

  1. Wedge action: The adjuster mechanism utilizes a wedge-shaped component called a star wheel or an adjuster screw assembly. As you apply the brakes repeatedly over time, this star wheel, which acts as the drum friction surface, rotates due to contact with other parts within the system. This rotation causes it to move outward or inward, adjusting the position of the brake shoes accordingly. The anchor pin ensures that the drum spins smoothly during this step.
  2. Friction material wear: As you use your vehicle’s brakes regularly, friction material on the brake shoes gradually wears down. This wear reduces the distance between the shoe and drum surfaces, affecting the automatic adjustment of various components within the adjuster mechanism.

Role of specific components in facilitating self-adjustment

Several components, including the wheel cylinder, notched wheel, and secondary shoe, work together within the rear drum brakes to facilitate self-adjustment.

  • The anchor pin is a crucial part of the star wheel/adjuster screw assembly. This step-shaped component rotates when the brakes are applied, adjusting the shoe-to-drum clearance. See the rear image for a visual representation.
  • The self-adjuster lever, connected to the star wheel, helps transmit motion and force to adjust the rear drum brakes and rear disc brakes. It plays a crucial role in maintaining the optimal contact between the brake shoes and the drum friction surface.
  • The adjusting spring, which provides tension and assists in returning the self-adjuster lever to its original position after adjustment, is an essential component of the emergency brake system. It works in conjunction with the wheel cylinder and rear brakes to ensure proper functioning. Additionally, it helps maintain the correct positioning of the secondary shoe, further enhancing the overall performance of the braking system.
  • Parking brake mechanism: The parking brake system is integrated into drum brakes. When you engage the parking brake, it activates a separate set of mechanisms that hold the brake shoes in a fixed position, preventing further adjustment. This mechanism includes the wheel cylinder, notched wheel, and step. See the image for a visual representation.

By combining the wheel cylinder, notched wheel, secondary shoe, and utilizing both mechanical forces and friction material wear, drum brakes can effectively self-adjust over time. This feature ensures consistent braking performance and compensates for any changes that may occur due to normal usage or wear. See the image below for a visual representation.

The process behind drum brake self-adjustment

  1. Initial adjustment: When the drum brakes are first installed, they need to be manually adjusted to ensure proper operation. This involves setting the clearance between the brake shoes and the drum.
  2. Brake application: As you press the brake pedal, hydraulic pressure is exerted on the wheel cylinder, causing it to expand. This expansion pushes the brake shoes outward against the inner surface of the drum.
  3. Contact with the drum: The friction material on the brake shoes makes contact with the rotating drum, generating friction that slows down or stops the rotation of the wheel.
  4. Self-adjustment mechanism engagement: Inside each wheel’s braking system, there is a star wheel adjuster mechanism. This mechanism consists of a threaded rod with a star-shaped gear at one end and an adjusting lever at the other end.
  5. Star wheel movement: When you apply and release your brakes repeatedly while driving, this causes slight backward movement of each shoe within its anchor points due to spring tension. Simultaneously, every time you reverse direction, it leads to incremental forward movement of each shoe.
  6. Adjuster lever action: The forward and backward movements of each shoe engage with their respective adjusting levers connected to them. These levers interact with the star wheels by pushing or pulling them according to their movements.
  7. Star wheel adjustment: As each shoe moves back and forth during regular braking operations, it engages with its adjuster lever which rotates or turns its corresponding star wheel in a specific direction depending on whether it needs tightening or loosening.
  8. Tightening or loosening: When a shoe moves outward (towards its anchor point), it tightens against the drum surface due to friction generated by braking force applied through hydraulic pressure from master cylinder pistons via wheel cylinders. Conversely, when a shoe moves inward (away from its anchor point), it loosens the contact with the drum.
  9. Automatic adjustment: The star wheel adjuster mechanism continuously adjusts the position of each brake shoe based on its movement and positioning during regular braking operations. This ensures that the optimal clearance between the shoes and drum is maintained, allowing for efficient and effective braking performance.

Description of the role played by the star wheel adjuster mechanism

The star wheel adjuster mechanism is a crucial step in drum brakes’ self-adjustment process. It consists of a threaded rod with a star-shaped gear at one end and an adjusting lever at the other end. The purpose of this mechanism is to regulate the movement and positioning of the brake shoes to maintain proper clearance between them and the drum. This image shows the star wheel adjuster mechanism in action. You can find more information on how to use it on WikiHow.

When you apply and release your brakes while driving, it causes slight movements of each shoe within its anchor points due to spring tension. These movements engage with their respective adjusting levers connected to them. As a result, the adjuster levers interact with their corresponding star wheels, which rotate or turn in response to these movements. This step is crucial in the brake system. The image below illustrates the process. You can find more detailed instructions on how to perform this step on the wikiHow website.

Signs that indicate the need for drum brake adjustment

Common symptoms suggesting a need for manual adjustment in drum brakes

  1. Brake pedal feels soft or spongy: If you notice that your brake pedal has lost its firmness and requires more pressure to engage, it could be a sign that your drum brakes need manual adjustment. Over time, the brake shoes inside the rear drums can wear down, causing the pedal to feel less responsive.
  2. Increased stopping distance: When your drum brakes are in need of adjustment, you may experience a longer stopping distance than usual. This occurs because worn-out brake shoes fail to generate sufficient friction against the drums, reducing their effectiveness.
  3. Drum spins freely after applying brakes: A clear indication that your drum brakes require adjustment is when you apply pressure to the brake pedal, but the rear drums continue spinning freely without slowing down. This suggests that the brake shoes are not making proper contact with the drums and need readjustment.
  4. Unusual noises while braking: If you hear grinding, squealing, or scraping noises when applying your brakes, it could be due to excessive wear on the brake shoes or an improper alignment of the rear drums. These sounds serve as warning signs that manual adjustment is necessary.

Warning signs that indicate potential issues with self-adjusting mechanisms

  1. Uneven braking performance: One of the key benefits of self-adjusting mechanisms in drum brakes is maintaining even wear on all components for consistent braking performance. However, if you notice uneven braking where one wheel locks up before others or experiences reduced stopping power, it may indicate a malfunction in the self-adjusting mechanism.
  2. Excessive vibration during braking: When self-adjusting mechanisms fail to function correctly, they can result in uneven contact between the brake shoes and drums. This can lead to vibrations felt through the steering wheel or brake pedal when braking at higher speeds. If you experience this, it’s crucial to have your drum brakes inspected and adjusted manually.
  3. Brake warning light illuminates: Some vehicles are equipped with a brake warning light on the dashboard that indicates potential issues with the braking system. If this light comes on, it could signal a problem with the self-adjusting mechanism in your drum brakes. It’s essential not to ignore this warning and have your brakes checked promptly.

Importance of recognizing early indicators to prevent further damage

Recognizing the signs that indicate the need for drum brake adjustment is a vital step for preventing further damage to your braking system. Ignoring these indicators can lead to more severe issues, such as damaging your brakes. This wikiHow article will guide you on how to recognize and address these signs effectively.

  1. Premature wear: When drum brakes are not properly adjusted, certain components may wear out faster than others due to uneven contact or excessive heat buildup. This can result in costly repairs or replacements down the line.
  2. Reduced braking performance: Inadequate adjustment of drum brakes compromises their ability to generate sufficient friction against the drums, leading to reduced stopping power and longer stopping distances. This poses a significant safety risk for both you and other drivers on the road.
  3. Damage to other brake components

Importance of regular drum brake maintenance

Regular maintenance of drum brakes is a crucial step in ensuring optimal performance and safety on the road. Neglecting routine maintenance can lead to decreased braking efficiency and compromised safety, putting both you and other drivers at risk. By adjusting your drum brakes according to the guidelines on WikiHow, including the drums, shoes, and other components, you can enjoy several benefits and avoid potential issues down the line.

how to adjust drum brakes without removing wheel

Explanation on why routine maintenance is crucial for optimal performance

Drum brakes are an essential step in your vehicle’s braking system. They rely on friction to adjust and slow down or stop your vehicle when you press the brake pedal. Over time, due to constant use and exposure to heat, dust, and moisture, these components can wear out or become less effective. To fix this issue, you can follow the instructions on WikiHow.

Regular maintenance, as explained on wikiHow, helps adjust your drum brakes and keep them in top condition. It allows you to identify issues early on, such as worn-out brake pads or leaking hydraulic fluid. By catching these problems early, you can prevent further damage to the braking system and avoid costly repairs in the future.

Benefits derived from keeping drums, shoes, and other components well-maintained

  1. Enhanced braking performance: Adjusting well-maintained drum brakes according to WikiHow guidelines provides better stopping power when you need it most. Regular inspections ensure that all components are functioning correctly and that there is sufficient pad material left for efficient braking.
  2. Adjusting your drum brakes regularly is essential for extending their lifespan. Following the steps on WikiHow can help you properly maintain them, preventing premature wear. Promptly replacing worn-out brake shoes is crucial to prevent damage to other parts of the system, such as drums or wheel cylinders.
  3. Cost savings: Regular upkeep, including inspections and minor adjustments, reduces the likelihood of major repairs or replacements to the wheel drum down the line. By investing in these wikihow tips now, you can save significant money in the long run.
  4. Safety: Adjusting your drum brakes ensures that they are operating at their best capacity during emergency situations where quick stops are necessary. This improves overall road safety for both you and other drivers. Learn how to adjust drum brakes on WikiHow.

Impact on overall braking efficiency and safety when neglecting maintenance

Neglecting drum brake maintenance can have severe consequences on your vehicle’s braking efficiency and safety. To ensure proper functioning, it is important to regularly adjust your drum brakes. If you’re unsure how to do this, WikiHow has a helpful guide that provides step-by-step instructions. Here are some potential issues that may arise if you fail to adjust your drum brakes.

  1. Reduced stopping power: Over time, worn-out brake shoes can lead to decreased braking performance, resulting in longer stopping distances. This can be dangerous, especially in emergency situations where every inch counts. To address this issue, it is important to regularly adjust the wheel drum according to the instructions provided on WikiHow.
  2. Lack of maintenance may cause uneven wear on the brake shoes or drums, which can affect your ability to control the vehicle effectively. If you experience vibrations or pulsations when applying the brakes, it’s important to adjust them properly. You can find step-by-step instructions on how to do this on wikiHow.
  3. Brake fade: Neglected drum brakes are more prone to overheating during prolonged or heavy braking, leading to a phenomenon known as brake fade. To adjust and prevent brake fade, you can follow the steps provided on WikiHow. Brake fade reduces the effectiveness of the brakes and increases the risk of accidents.
  4. Failing to adjust drum brakes properly compromises your safety and that of others on the road. Inadequate braking performance puts you at a higher risk of collisions or being unable to stop in time to avoid obstacles. To ensure your safety, it is important to maintain drum brakes according to the instructions provided by wikiHow.

Step-by-step guide to locating the rubber plug on a drum brake

Detailed instructions on finding and accessing the rubber plug for adjustments

Here’s a step-by-step guide to help you find and access the rubber plug on your drum brake.

  1. Prepare your tools: Before you begin, gather all the necessary tools for this task. You’ll need a lug wrench or socket set to remove the lug nuts, a flat head screwdriver, and possibly a brake spoon for adjusting the brake shoes.
  2. Secure your vehicle: Park your vehicle on level ground and engage the parking brake. If you’re working on one wheel at a time, use wheel chocks or blocks to prevent any movement.
  3. Remove the wheel: Loosen the lug nuts with your lug wrench or socket set before raising your vehicle using a jack. Once lifted, remove the lug nuts completely and take off the rear wheel.
  4. Locate the drum brake assembly: With the wheel removed, you’ll now have clear visibility of the drum brake assembly. Look for a circular metal cover on its backing plate; this cover houses the rubber plug we’re searching for.
  5. Identify different types and locations of rubber plugs: Rubber plugs can vary in appearance depending on their design and manufacturer specifications. Some may have indentations or grooves that make them easier to grip when removing or replacing them.
  6. Remove or replace rubber plugs with caution: Using a flat head screwdriver, carefully pry out or unscrew the rubber plug from its housing in order to access the adjustment mechanism beneath it. Exercise caution not to damage or distort it during this process.
  7. Inspect and adjust as needed: Once you’ve successfully accessed the adjustment mechanism, you can inspect and adjust the brake shoes. A brake spoon is a helpful tool for this task, allowing you to turn the star wheel or adjuster bolt to increase or decrease the tension on the brake shoes.

Tips for identifying different types and locations of rubber plugs

Identifying different types and locations of rubber plugs can be challenging, especially if you’re unfamiliar with drum brakes. Here are some useful tips from wikiHow to help you adjust in this process.

  • Consult your vehicle’s manual to adjust your vehicle. Your vehicle’s manual should provide information about the location and appearance of rubber plugs specific to your model.
  • Online resources like WikiHow offer detailed guides with illustrations that can assist in locating and adjusting rubber plugs on various vehicles.
  • Visual inspection: Take a close look at your drum brake assembly and adjust if necessary. Rubber plugs are typically found on the backing plate, near where the anchor pin or return springs are located.

Importance of caution while removing or replacing rubber plugs

Exercising caution is crucial. Here’s why:

  • Prevent damage: Rubber plugs may become brittle over time due to exposure to heat and other environmental factors. It is important to regularly adjust rubber plugs to ensure their longevity.

Ensuring optimal performance with drum brake self-adjustment

Best practices to follow after adjusting drum brakes

drum brake adjustment direction

Adjusting drum brakes is an essential maintenance task that helps ensure optimal performance and safety. Once you’ve completed the adjustment process, it’s crucial to follow a few best practices to make sure everything is in proper working order.

  1. Inspect the brake system: After adjusting the drum brakes, take a moment to visually inspect the entire brake system. Look for any signs of damage or wear on components such as the wheel drums, adjusters, wheel cylinder pistons, and lever assembly. If you notice any issues, address them promptly to prevent further complications.
  2. Test the parking brake: The parking brake is an integral part of the drum brake system. After adjusting the brakes, engage the parking brake and test its functionality. Ensure that it engages smoothly and holds your vehicle securely in place without any slippage.
  3. Check for proper adjustment: To verify that your drum brakes are correctly adjusted, perform a quick test by pressing on the brake pedal while driving at low speed (in a safe area). If you feel excessive resistance or dragging when applying the brakes, it could indicate over-adjustment. On the other hand, if there is little resistance or inadequate braking power, under-adjustment may be an issue.

Tips for testing and verifying proper functioning post-adjustment

To guarantee your drum brakes are working optimally after adjustment, consider these tips for testing and verifying their proper functioning:

  1. Perform a road test: Take your vehicle for a short drive around your neighborhood or another suitable area where you can safely test its braking performance. Pay attention to how quickly your vehicle comes to a stop when applying light pressure on the pedal versus firm pressure.
  2. Listen for abnormal noises: While driving during your road test, listen carefully for any unusual noises coming from your wheels or braking system. Squealing, grinding, or metallic sounds could indicate a problem with the drum friction surface or other brake components.
  3. Observe wheel behavior: Keep an eye on your wheels during braking. If you notice one wheel locking up before the others or uneven tire wear, it may indicate an issue with the adjustment on that particular wheel.

Recommendations for ongoing monitoring and periodic rechecks

To ensure long-term performance and safety, it’s important to establish a routine for monitoring and periodically rechecking your drum brakes’ adjustment. Here are some recommendations to follow:

  1. Regular visual inspections: Make it a habit to visually inspect your drum brakes regularly. Look for signs of wear, damage, or fluid leaks around the wheel cylinders and master cylinder. Check the adjuster mechanisms for proper operation.
  2. Monitor brake pedal feel: Pay attention to how your brake pedal feels when you apply pressure. If it becomes spongy or sinks too close to the floor before engaging the brakes, it could indicate air in the system or other issues that require attention.
  3. Check parking brake effectiveness:


Understanding how drum brakes self-adjust is crucial for maintaining optimal performance and safety in your vehicle. By exploring the process behind drum brake self-adjustment, recognizing signs that indicate the need for adjustment, and emphasizing the importance of regular maintenance, you can ensure your drum brakes are functioning at their best.

Regularly inspecting your drum brakes and locating the rubber plug is a key step in the self-adjustment process. This simple action can help prevent issues such as excessive wear or reduced braking efficiency. By taking the time to perform these checks, you can save yourself from potential accidents and costly repairs down the line.

Frequently Asked Questions

How often should I check my drum brakes for adjustment?

It is recommended to check your drum brakes for adjustment every 6 months or every 10,000 miles driven.

What are some signs that indicate my drum brakes need adjustment?

Signs that may indicate the need for drum brake adjustment include a soft or spongy pedal feel, longer stopping distances, or an audible scraping noise during braking.

Can I adjust my own drum brakes?

While it is possible to adjust your own drum brakes with some mechanical knowledge and the right tools, it is advisable to consult a professional mechanic if you’re unsure about the process.

Are self-adjusting drum brakes more reliable than manual adjustment?

Self-adjusting drum brakes can help maintain proper brake shoe-to-drum clearance automatically, reducing the need for manual adjustments. This can lead to more consistent and reliable braking performance.

Can I drive with drum brakes that are out of adjustment?

Driving with drum brakes that are out of adjustment can compromise your vehicle’s braking ability and pose a safety risk. It is essential to address any issues promptly by adjusting or repairing the drum brakes as needed.