How to Adjust Drum Brakes: A Comprehensive Guide

Drum brakes, while less common on modern vehicles, are still found on many cars, trucks, and trailers, particularly on the rear wheels. Knowing how to adjust them is a valuable skill for any DIY mechanic. Proper adjustment ensures optimal braking performance, safety, and extends the life of your brake components. This comprehensive guide provides a step-by-step process for adjusting drum brakes, along with essential safety precautions and helpful tips.

Why Adjust Drum Brakes?

Unlike disc brakes, which are self-adjusting in most modern applications, drum brakes require periodic manual adjustment. Here’s why:

* **Maintain Optimal Braking Performance:** As brake shoes wear down, the distance between the shoes and the drum increases. This increased distance results in a longer pedal travel and reduced braking force. Adjusting the brakes brings the shoes closer to the drum, restoring optimal braking response.
* **Prevent Uneven Braking:** Unevenly adjusted drum brakes can cause the vehicle to pull to one side during braking, creating a dangerous situation. Proper adjustment ensures that each brake is applying equal force.
* **Extend Brake Component Life:** Letting the brakes remain out of adjustment can cause excessive wear on the brake shoes, drums, and other related components. Regular adjustment prevents premature wear and saves you money on repairs.
* **Proper Parking Brake Functionality:** In many vehicles, the parking brake utilizes the drum brake mechanism. A properly adjusted drum brake is crucial for the parking brake to hold the vehicle securely.

Safety First! Essential Precautions

Before you begin, prioritize your safety. Always take these precautions:

* **Wear Safety Glasses:** Protect your eyes from dust, debris, and brake cleaner spray.
* **Wear Gloves:** Brake dust can contain asbestos (in older vehicles) and other harmful substances. Wear gloves to protect your skin.
* **Work in a Well-Ventilated Area:** Brake cleaner and other chemicals can release harmful fumes. Ensure adequate ventilation.
* **Use Jack Stands:** Never work under a vehicle supported only by a jack. Use sturdy jack stands to secure the vehicle.
* **Chock the Wheels:** Place wheel chocks behind the wheels that remain on the ground to prevent the vehicle from rolling.
* **Refer to Your Vehicle’s Service Manual:** Always consult your vehicle’s service manual for specific instructions and torque specifications.
* **Disconnect the Negative Battery Terminal:** Disconnecting the negative battery terminal prevents accidental electrical shorts during the adjustment process. Especially important if working near ABS sensors.

Tools You’ll Need

* **Jack and Jack Stands:** To safely lift and support the vehicle.
* **Wheel Chocks:** To prevent the vehicle from rolling.
* **Lug Wrench:** To remove the wheels.
* **Screwdriver (Flat-Head):** For accessing the adjustment mechanism.
* **Brake Adjustment Tool (Spoon):** Specifically designed to adjust drum brakes. While a screwdriver *can* be used, a brake adjustment tool provides better leverage and control.
* **Penetrating Oil (Optional):** To loosen any rusty or seized components.
* **Brake Cleaner:** To clean brake components.
* **Torque Wrench:** To tighten the lug nuts to the correct specification.
* **Gloves and Safety Glasses:** For personal protection.
* **Service Manual:** For specific instructions and torque specifications for your vehicle.

Step-by-Step Guide to Adjusting Drum Brakes

This guide provides a general overview of the drum brake adjustment process. Always refer to your vehicle’s service manual for specific instructions and torque specifications.

**Step 1: Prepare the Vehicle**

1. **Park on a Level Surface:** Ensure the vehicle is parked on a flat and stable surface.
2. **Engage the Parking Brake:** Engage the parking brake to prevent the vehicle from rolling while you loosen the lug nuts. Then, disengage the parking brake before lifting the vehicle.
3. **Loosen the Lug Nuts:** Use a lug wrench to loosen the lug nuts on the wheel you’ll be working on. Do not remove them completely at this stage.
4. **Chock the Rear Wheels:** Place wheel chocks behind the rear wheels (if working on the front) or in front of the front wheels (if working on the rear).
5. **Lift the Vehicle:** Use a jack to lift the vehicle until the tire is off the ground.
6. **Secure with Jack Stands:** Immediately place jack stands under the vehicle’s frame or designated jacking points. Never work under a vehicle supported only by a jack.
7. **Remove the Wheel:** Finish removing the lug nuts and carefully remove the wheel.

**Step 2: Locate the Adjustment Mechanism**

Drum brakes typically have an adjustment mechanism that allows you to increase or decrease the distance between the brake shoes and the drum. The location of this mechanism can vary depending on the vehicle make and model, but it is commonly found in one of two locations:

* **Through a Slot in the Backing Plate:** Most drum brakes have an access slot in the backing plate (the metal plate behind the drum). This slot is usually covered by a rubber or plastic plug.
* **Integrated into the Parking Brake Lever:** Some vehicles integrate the adjustment mechanism into the parking brake lever assembly inside the drum.

**Locating the Adjustment Slot:**

1. **Inspect the Backing Plate:** Carefully examine the backing plate for a small oval or rectangular slot. It’s usually located near the bottom of the backing plate.
2. **Remove the Plug:** If you find a slot, use a screwdriver or pick to carefully remove the rubber or plastic plug covering the slot. The plug may be brittle and break easily, so be gentle.

**Step 3: Adjusting the Brakes Through the Backing Plate Slot**

This is the most common method for adjusting drum brakes.

1. **Insert the Brake Adjustment Tool:** Insert the brake adjustment tool (or a flat-head screwdriver) into the adjustment slot. You should be able to feel the toothed wheel of the adjuster mechanism.
2. **Determine the Adjustment Direction:** The direction you need to turn the adjustment wheel depends on whether you are working on the left or right side of the vehicle. You’ll be either expanding or contracting the brake shoes. Here’s a general rule:
* **General Rule:** To tighten the brakes (bring the shoes closer to the drum), you usually need to move the tool upwards on one side of the vehicle and downwards on the other. However, it is best to check a repair manual for the specific vehicle to be absolutely certain of the proper direction.
* **Testing the Direction:** If you’re unsure, start by turning the adjustment wheel a few clicks in one direction. Then, try to spin the brake drum by hand. If the drum spins more freely, you’re turning it the wrong way. If it becomes harder to spin, you’re going in the right direction. Important: You are looking to turn the star wheel to make the brakes slightly contact the inside surface of the drum, not lock the drum.
3. **Adjust the Brakes:** Turn the adjustment wheel a few clicks at a time. After each adjustment, try to spin the brake drum by hand. You should feel a slight drag as the brake shoes contact the drum. The goal is to adjust the brakes until there is a slight drag, but the drum can still be rotated by hand. Do not overtighten.
4. **Avoid Overtightening:** Overtightening the brakes can cause them to bind and overheat, leading to premature wear and potential brake failure. If you overtighten the brakes, you will need to back off the adjustment until the drum spins freely with a slight drag.
5. **Repeat on the Other Side:** Repeat the adjustment process on the other brake drum on the same axle. It’s crucial to adjust both brakes equally to ensure even braking performance.

**Step 4: Adjusting Brakes Integrated with the Parking Brake Lever (Less Common)**

This type of adjustment is less common but found on some vehicles.

1. **Locate the Parking Brake Lever:** Inside the drum, locate the parking brake lever. It’s typically connected to the parking brake cable.
2. **Identify the Adjustment Mechanism:** Look for an adjustment screw or wheel near the parking brake lever.
3. **Adjust the Brakes:** Use a screwdriver or wrench to turn the adjustment screw or wheel. The goal is the same as with the backing plate adjustment: to achieve a slight drag on the drum when it’s rotated by hand.
4. **Refer to Service Manual:** Always consult your vehicle’s service manual for specific instructions on adjusting brakes with an integrated parking brake lever.

**Step 5: Final Checks and Reassembly**

1. **Ensure Equal Drag:** After adjusting both brakes, spin each drum by hand. They should both have a similar amount of drag. If one brake is significantly tighter than the other, readjust them until they are even.
2. **Reinstall the Adjustment Slot Plug:** Replace the rubber or plastic plug in the backing plate adjustment slot to prevent dirt and moisture from entering the brake assembly. If the old plug is damaged or missing, replace it with a new one.
3. **Mount the Wheel:** Carefully mount the wheel back onto the hub.
4. **Tighten the Lug Nuts:** Hand-tighten the lug nuts in a star pattern.
5. **Lower the Vehicle:** Carefully lower the vehicle until the tire touches the ground, but the full weight of the vehicle is not yet on the tire.
6. **Torque the Lug Nuts:** Use a torque wrench to tighten the lug nuts to the manufacturer’s specified torque specification. Tighten them in a star pattern to ensure even pressure.
7. **Lower the Vehicle Completely:** Lower the vehicle completely to the ground.
8. **Test the Brakes:** Before driving, pump the brake pedal several times to seat the brake shoes and drums. Then, perform a test drive at low speeds to ensure the brakes are functioning correctly. Pay attention to any unusual noises or pulling to one side during braking.

**Step 6: Fine-Tuning the Parking Brake (If Necessary)**

After adjusting the drum brakes, you may need to fine-tune the parking brake cable. Here’s how:

1. **Locate the Parking Brake Cable Adjuster:** The parking brake cable adjuster is typically located under the vehicle, near the center, where the parking brake cables converge.
2. **Adjust the Cable Tension:** Use a wrench to adjust the cable tension until the parking brake lever engages with the correct number of clicks (refer to your service manual for the specified number of clicks).
3. **Test the Parking Brake:** Engage the parking brake on a slight incline to ensure it holds the vehicle securely. If it doesn’t, readjust the cable tension as needed.

Troubleshooting Common Issues

* **Brakes Still Don’t Feel Right:** If the brakes still don’t feel right after adjustment, it could indicate other problems, such as worn brake shoes, damaged drums, or a faulty brake cylinder. In this case, it’s best to consult a qualified mechanic.
* **Cannot Turn the Adjustment Wheel:** If the adjustment wheel is seized or difficult to turn, try applying penetrating oil to the mechanism and let it soak for a while. If it still won’t turn, you may need to disassemble the brake assembly for cleaning and repair.
* **Brakes are Noisy:** Noisy brakes can be caused by various factors, including worn brake shoes, glazed drums, or loose hardware. Inspect the brake components carefully and replace any worn or damaged parts.
* **Brakes are Grabbing:** Grabbing brakes can be caused by contamination of the brake shoes with oil or grease, or by a faulty brake cylinder. Clean the brake shoes and drums with brake cleaner and replace any faulty components.

Tips for Successful Drum Brake Adjustment

* **Work on a Level Surface:** Always work on a level surface to ensure accurate adjustments.
* **Use Quality Tools:** Using high-quality tools will make the job easier and safer.
* **Don’t Overtighten:** Overtightening the brakes can cause them to bind and overheat.
* **Cleanliness is Key:** Keep the brake components clean to prevent contamination.
* **Inspect Regularly:** Inspect your drum brakes regularly for wear and damage.
* **When in Doubt, Seek Professional Help:** If you’re not comfortable adjusting drum brakes yourself, it’s always best to seek professional help.
* **Consider Replacing Springs:** When the drum is off for adjustment, and the vehicle is older, consider replacing the springs. Springs lose tension over time, and new springs will keep everything tight.
* **Lubricate Moving Parts:** Use brake grease to lubricate the backing plate contact points and the star wheel threads. This helps prevent seizing and ensures smooth operation.
* **Check Brake Lines and Hoses:** While you’re working on the brakes, inspect the brake lines and hoses for any signs of leaks, cracks, or damage. Replace any damaged lines or hoses immediately.
* **Take Pictures:** Before disassembling anything, take pictures of the brake assembly. This can be helpful when reassembling the brakes.

When to Replace Drum Brake Components

Adjusting your drum brakes will not fix worn out or damaged components. You should replace your drum brake components if you observe any of the following:

* **Worn Brake Shoes:** If the brake shoe lining is worn down to the rivets or metal backing, it’s time to replace them. A good rule of thumb is if they are less than 1/8″ thick they need replacing.
* **Damaged Brake Drums:** If the brake drums are cracked, warped, or scored, they should be replaced. A machine shop may be able to resurface the drums if the damage is minor, but always follow the manufacturer’s specifications.
* **Leaking Wheel Cylinders:** If the wheel cylinders are leaking brake fluid, they need to be replaced immediately. Leaking fluid will contaminate the brake shoes and reduce braking performance.
* **Broken or Worn Springs:** If any of the brake springs are broken, weak, or corroded, they should be replaced. Weak springs can cause uneven brake wear and reduce braking performance.
* **Seized or Damaged Hardware:** Replace any seized, bent, or otherwise damaged hardware such as the self-adjuster mechanism, hold-down pins, or levers.

Conclusion

Adjusting drum brakes is a relatively straightforward process that can significantly improve your vehicle’s braking performance and safety. By following the steps outlined in this guide and taking the necessary safety precautions, you can confidently adjust your drum brakes and keep your vehicle running smoothly. Remember to always consult your vehicle’s service manual for specific instructions and torque specifications. Regular maintenance and timely repairs will ensure that your braking system is always in top condition, providing you with safe and reliable stopping power.