Do Drum Brakes Need Adjusting? Your UK Guide

While modern vehicles frequently feature disc brakes on all four wheels, many cars, especially older models or those at the rear, still rely on drum brakes. These robust braking systems are designed to be largely self-adjusting, a clever mechanism that typically operates when you engage reverse gear and apply the brakes. However, relying solely on this automatic function might not always suffice. There are crucial instances when manual adjustment becomes not just beneficial, but absolutely necessary, to ensure your vehicle's braking performance remains safe and effective. Understanding when and how to perform this adjustment is a fundamental aspect of car maintenance that can significantly impact your stopping distance and overall road safety.

Properly adjusted drum brakes contribute immensely to a balanced and responsive braking system. An imbalance, or excessive travel in the brake pedal, can be a clear indicator that your drum brakes are not performing optimally. Unlike disc brakes, which typically self-adjust every time they are used and only require manual intervention if components like calipers are removed or replaced, drum brakes, despite their self-adjusting design, can sometimes 'forget' to keep up with wear. This can lead to a spongy pedal, reduced braking efficiency, and even uneven braking, pulling your vehicle to one side during a stop. Addressing these issues proactively is vital for both your safety and the longevity of your braking components.

Understanding Your Drum Brakes and Their Self-Adjustment

Drum brakes operate on a simple yet effective principle: brake shoes press outwards against the inside of a spinning drum, creating friction that slows the wheel. Over time, the brake shoes wear down, increasing the gap between the shoes and the drum. To compensate for this wear, most drum brake systems incorporate an automatic adjuster, often a star wheel mechanism, which is designed to incrementally expand the shoes. This adjustment typically occurs when the vehicle is driven in reverse and the brakes are applied. The momentum of the vehicle, combined with the brake application, activates a lever that rotates the star wheel, taking up any slack. While this system is generally reliable, it's not infallible. Factors such as infrequent use of reverse, light braking, or even corrosion can hinder the self-adjustment mechanism, necessitating manual intervention.

Why Manual Adjustment Becomes Necessary

Even with their self-adjusting capabilities, drum brakes can often benefit from, or even require, manual adjustment. Here are the primary scenarios where you'll need to reach for your tools:

• New Brake Shoes or Drums: Whenever you replace your brake shoes or the brake drums themselves, the system starts with a significant gap. While the self-adjusters will eventually catch up, manual adjustment immediately after replacement ensures optimal performance from the outset and prevents excessive pedal travel.
• Excessive Brake Pedal Travel: If your brake pedal feels 'spongy' or travels too far towards the floor before the brakes engage effectively, it’s a strong indicator that your drum brakes are not sufficiently adjusted. This excessive travel means the shoes have to move a greater distance before contacting the drum, leading to delayed and less efficient braking.
• Parking Brake Issues: The parking brake (or handbrake) system often operates directly on the rear drum brakes. If your parking brake cable feels loose, or if the parking brake doesn't hold the vehicle securely, it could be a sign that the drum brakes themselves are out of adjustment. Proper drum brake adjustment is a prerequisite for a functional parking brake.
• Uneven Braking: If your vehicle pulls to one side when you apply the brakes, it could be due to uneven adjustment between the left and right drum brakes. One side might be engaging more effectively than the other, causing the vehicle to veer.
• After Disassembly: If any part of the drum brake assembly has been taken apart for inspection, cleaning, or repair, a manual adjustment is highly recommended to ensure everything is correctly re-tensioned.

Tools and Safety Precautions Before You Begin

Before you even think about touching your vehicle's braking system, safety must be your absolute priority. Working under a vehicle carries inherent risks, and improper procedures can lead to serious injury or damage. Gather all your tools beforehand and ensure you have a safe, level workspace.

Essential Tools:

• Vehicle Jack: A sturdy hydraulic jack capable of safely lifting your vehicle.
• Axle Stands (Jack Stands): Crucial for supporting the vehicle once it's lifted. Never rely solely on a jack.
• Wheel Chocks: To prevent the vehicle from rolling while it's jacked up.
• Wheel Brace (Lug Wrench): For removing wheel nuts.
• Flat-Head Screwdrivers (Two): Preferably one long and thin, and another standard length. These are your primary tools for manipulating the adjuster.
• Brake Cleaner: Useful for cleaning any dust or debris.
• Safety Goggles: To protect your eyes from brake dust and debris.
• Gloves: To protect your hands from grease and brake dust, which can contain harmful fibres.
• Torch (Flashlight): For better visibility under the vehicle.

Safety First:

Always adhere to these safety guidelines:

• Park on a Level Surface: Ensure your vehicle is on a firm, flat, and level surface.
• Engage Parking Brake and Chock Wheels: Even though you'll be adjusting the rear brakes, engage the parking brake (if it's working) and place wheel chocks on the wheels that will remain on the ground (e.g., front wheels if working on the rear).
• Use Axle Stands: Once the vehicle is lifted with the jack, immediately place axle stands securely under the vehicle's designated jacking points. Lower the vehicle onto the stands. Never work under a vehicle supported only by a jack.
• Wear PPE: Always wear safety goggles and gloves. Brake dust can be harmful if inhaled or gets into your eyes.
• Allow Brakes to Cool: If you've just driven the car, allow the brakes to cool down before working on them. Hot components can cause burns.
• Consult Your Vehicle Manual: Always refer to your vehicle's specific service manual for precise jacking points and any model-specific information regarding brake adjustment.

Step-by-Step Guide to Adjusting Your Drum Brakes

With safety measures in place and tools at hand, you're ready to tackle the adjustment process. Remember to work on one wheel at a time, or at least one side at a time, to ensure consistency.

1. Initial Tyre Rotation Check

Before any adjustment, it's crucial to assess the current state of your drum brakes. With the vehicle safely on axle stands and the wheel still attached, give the tyre a good spin by hand. Observe how many revolutions it makes before it naturally comes to a stop due to the internal drag of the brake shoes. Ideally, a properly adjusted drum brake will allow the tyre to spin between one and a half to three full rotations. If it spins much more freely, the brakes are likely too loose. If it barely spins, they might be too tight, or there could be another issue.

2. Locating the Adjuster Cutout

The drum brake adjuster is accessed through a small cutout on the brake backing plate, which is the large metal plate behind the brake drum. This cutout is typically located near the bottom of the backing plate and is usually sealed with a rubber plug to keep out dirt and moisture. Use your torch to locate this plug. Carefully remove the rubber plug; you might need a small flat-head screwdriver or a pick tool to pry it out.

3. Manipulating the Adjuster Mechanism

Once the plug is removed, you'll see a small opening. Inside this opening, you'll need to locate the star wheel adjuster and the automatic adjustment lever. This is where your two flat-head screwdrivers come into play:

• Releasing the Lever: Insert one flat-head screwdriver into the hole. Your goal is to push the small lever (often spring-loaded) that rests against the teeth of the star wheel. This lever is what prevents the star wheel from rotating freely and is part of the self-adjusting mechanism. You need to gently push this lever away from the star wheel to allow it to turn.
• Turning the Star Wheel: While holding the lever away with the first screwdriver, insert your second flat-head screwdriver into the hole. Use this second screwdriver to engage the teeth of the star wheel.

Now, you need to decide which way to turn the star wheel:

• To Tighten (Reduce Pedal Travel): Rotate the star wheel in the direction that spreads the brake shoes further apart. This will reduce the gap between the shoes and the drum, making the brake pedal feel firmer and reducing its travel. You'll hear distinct clicks as you turn the wheel.
• To Loosen (Increase Tyre Spin): If you've overtightened or need to increase the gap, rotate the star wheel in the opposite direction.

Make small adjustments – typically a few clicks at a time. After a few turns, remove your screwdrivers, allow the lever to re-engage, and then spin the tyre again to check the rotation. The goal is to reach that 1.5 to 3 full rotations. If the tyre now spins too freely, you've gone too far in the loosening direction and need to turn the star wheel the other way to tighten it slightly. Conversely, if it's too tight and barely spins, loosen it slightly.

Remember, the more drag you put on the drum by tightening, the less the brake pedal will travel when stopping the car. However, excessive drag can also lead to premature wear of your brake shoes and drums, as well as potential overheating. It's a fine balance.

4. Centring the Brake Shoes

After adjusting the star wheel, it's good practice to 'centre' the brake shoes within the drum. This helps ensure even contact and prevents noise or uneven wear. You can typically achieve this by reaching behind the backing plate and gently pulling on the parking brake cable where it connects to the brake assembly. This action helps to seat the shoes properly against the anchor points and the drum.

5. Parking Brake Check and Adjustment

Once you've achieved the desired drum brake adjustment, it's critical to check the parking brake's function, as it often relies on the rear drum brakes. Engage the parking brake fully from inside the vehicle and then attempt to spin the adjusted tyre. It should be firmly locked and not spin at all. Repeat this on the other side of the vehicle.

If one tyre is holding with the parking brake applied and the other is not, or if the parking brake lever feels too loose or too tight, you may need to adjust the parking brake cable itself. This adjustment is usually found where the main parking brake cable splits into two separate cables, one for each rear wheel. This is typically located underneath the vehicle, often near the middle. Adjust the nut on the cable splitter until both rear wheels are equally held firm when the parking brake is engaged, and then release freely when disengaged.

6. Final Checks and Road Test

Before lowering the vehicle, ensure you replace the rubber plugs back into the cutouts on the backing plates. These plugs protect the adjuster mechanism from dirt, water, and debris. Double-check that all wheel nuts are torqued correctly. Lower the vehicle safely.

Finally, perform a cautious road test in a safe area. Start by driving slowly and gently applying the brakes to feel the pedal response. The pedal should feel firm and consistent. Make a few stops from low speed, then gradually increase your speed. Pay attention to any pulling, squealing, or unusual noises. If the pedal still feels spongy or too firm, or if there's any pulling, you may need to re-adjust one or both sides.

Troubleshooting Common Adjustment Issues

Even with careful execution, you might encounter some minor issues. Here's how to address them:

• Tyre Still Spins Too Freely: The brakes are still too loose. Re-jack the vehicle and tighten the star wheel adjuster a few more clicks.
• Tyre Barely Spins/Excessive Drag: The brakes are too tight. This can cause overheating and premature wear. Re-jack the vehicle and loosen the star wheel adjuster a few clicks.
• Brake Pedal Still Spongy: While drum brake adjustment helps, a spongy pedal can also indicate air in the brake lines, a failing master cylinder, or other hydraulic issues. If adjustment doesn't resolve it, a professional inspection is warranted.
• Uneven Braking/Pulling: This often points to one side being adjusted tighter than the other. Re-check the tyre spin on both sides and adjust as necessary to achieve balance. It could also indicate worn brake shoes, contaminated linings, or a seizing wheel cylinder, which would require more than just adjustment.

Maintenance Tips for Drum Brakes

Regular inspection and timely maintenance are crucial for the longevity and performance of your drum brakes:

• Regular Inspections: During tyre rotations or other under-car maintenance, visually inspect the drum brakes for signs of leakage (from the wheel cylinder), excessive rust, or damage to the backing plate.
• Brake Dust: Drum brakes generate a lot of dust. When performing major brake service, clean out accumulated dust using an approved brake cleaner spray (never compressed air without proper respiratory protection, as brake dust can contain asbestos fibres in older vehicles, though less common now).
• Listen for Noises: A grinding or squealing noise from the rear could indicate severely worn brake shoes or a problem with the drum itself.
• Fluid Checks: While not directly related to mechanical adjustment, ensure your brake fluid level is always correct and that the fluid is changed according to your vehicle manufacturer's recommendations. Low fluid or contaminated fluid affects overall braking performance.

Drum Brakes vs. Disc Brakes: A Quick Look at Adjustment

It's worth briefly noting the difference in adjustment between drum and disc brakes, as the initial information provided touched upon both. This table highlights the key distinctions:

Frequently Asked Questions About Drum Brake Adjustment

Q1: How often should drum brakes be adjusted?

A: Most modern drum brakes are designed to self-adjust, so a specific schedule for manual adjustment isn't usually provided. However, a manual adjustment is highly recommended whenever you install new brake shoes or drums, or if you notice symptoms like excessive brake pedal travel or a weak parking brake. It's also a good idea to check them during routine maintenance, perhaps every 10,000-15,000 miles, especially if your vehicle sees heavy use or infrequent reverse driving.

Q2: Can I adjust drum brakes myself?

A: Yes, adjusting drum brakes is a relatively straightforward DIY task for someone with basic mechanical aptitude and the correct tools. However, it's crucial to follow safety procedures diligently, especially regarding vehicle jacking and support. If you're unsure or uncomfortable, it's always best to consult a qualified mechanic.

Q3: What are the signs of poorly adjusted drum brakes?

A: Key signs include excessive brake pedal travel (the pedal goes too far down before the brakes engage), a 'spongy' or soft pedal feel, reduced braking efficiency, uneven braking (the vehicle pulls to one side when braking), or a weak or ineffective parking brake.

Q4: Does adjusting drum brakes improve braking performance?

A: Absolutely. Proper adjustment ensures that the brake shoes are optimally positioned close to the drum. This reduces the time it takes for the shoes to contact the drum when you press the pedal, leading to a firmer pedal feel, quicker brake response, and improved stopping distance. It also helps in achieving balanced braking across both rear wheels.

Q5: What happens if I over-adjust drum brakes?

A: Over-adjusting drum brakes means the shoes are too close to or constantly in contact with the drum. This creates excessive drag, leading to premature wear of the brake shoes and drums, overheating of the brakes (which can cause brake fade), and reduced fuel efficiency due to constant friction. The wheel may also be stiff to rotate or even lock up.

Q6: Are all drum brakes self-adjusting?

A: Most modern drum brakes are designed with an automatic self-adjusting mechanism. However, very old vehicles might have manually adjusted drum brakes without an automatic feature. Even with self-adjusting systems, factors like infrequent use of reverse or corrosion can hinder their effectiveness, necessitating manual intervention.

In conclusion, while your vehicle's drum brakes are engineered for a degree of self-sufficiency, understanding when and how to perform a manual adjustment is a valuable skill for any car owner. It's a relatively simple procedure that can significantly enhance your vehicle's braking performance, providing a firmer pedal, more responsive stops, and ultimately, greater safety on the road. By paying attention to the signs of maladjustment and taking the time to perform these checks, you're not just maintaining your car; you're actively contributing to a safer driving experience for yourself and others.

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