Rear drum brake systems are a common feature in many U.S. vehicles and require periodic maintenance or replacement of components such as brake shoes, springs, and wheel cylinders. This article provides step-by-step installation instructions and best practices based on information from verified technical resources. The guide covers disassembly, reassembly, adjustment, and testing procedures to ensure safe and effective brake operation after maintenance.
Introduction
Drum brake systems, while less common than disc brakes in modern vehicles, are still found in many rear-wheel setups. These systems rely on brake shoes that press against the inside of the drum to slow the vehicle. Over time, components like the shoes, springs, and wheel cylinders wear out and must be replaced. The process of replacing and adjusting rear drum brake shoes requires careful attention to detail to ensure the proper fit and function of the system.
The instructions and best practices outlined in this guide are drawn from multiple technical sources, including step-by-step guides and manufacturer-recommended procedures. The goal is to provide a clear, actionable reference for users performing this task on their own vehicles, emphasizing correct orientation, tension, and adjustment techniques.
Tools and Safety Considerations
Before beginning the installation process, gather the necessary tools and materials. The following items are typically required for rear drum brake shoe replacement:
- Floor jack and jack stands
- Lug wrench
- Brake cleaner
- Wire brush
- Anti-seize compound or brake grease
- Brake adjusting tool or large flathead screwdriver
- Needle-nose pliers
- Digital micrometer (optional, for measuring brake shoe thickness)
- New brake shoes
- New springs and pins (if necessary)
- New brake drum (if damaged)
- New wheel cylinder (if leaking)
Safety is a critical concern when working on brake systems. Always ensure the vehicle is securely supported on jack stands before beginning work. Avoid working with the vehicle resting on a floor jack alone. Additionally, wear appropriate protective gear, including gloves and safety glasses, to prevent exposure to brake dust and debris.
Disassembly and Inspection
Before installing new brake shoes, it is essential to disassemble the existing components and inspect them for damage or wear. Begin by removing the wheel and brake drum. If the drum is stuck, use the brake adjuster tool or a screwdriver to manually back off the adjuster wheel until the drum slides off.
Once the drum is removed, the internal components such as the brake shoes, springs, and wheel cylinder will be visible. Use brake cleaner to clean the assembly thoroughly and inspect the parts for wear. Pay particular attention to the thickness of the brake shoes: if they measure less than 1/16th of an inch, replacement is necessary. Inspect the wheel cylinder for leaks, as a faulty cylinder can lead to brake fluid loss and reduced braking efficiency.
Remove the brake shoes by first disconnecting the hold-down and return springs. These springs are under high tension, so caution is required during removal. Some vehicles use pins and washers in place of springs, which can also be removed using needle-nose pliers. Once the springs and pins are removed, the brake shoes can be taken off the backing plate.
After removing the shoes, the parking brake cable retainer clip should be addressed. Using a flathead screwdriver or pliers, remove the clip to access and inspect the parking brake mechanism. If the parking brake cable is damaged or worn, consider replacing it during this process.
Reassembly and Installation
With the old components removed and inspected, the next step is to install the new brake shoes and associated hardware. Begin by laying out the new shoes and identifying the primary and secondary shoes. The secondary shoe is typically thinner and has a shorter friction material and is installed toward the front of the vehicle. The primary shoe, which is thicker and has a longer friction material, is installed toward the rear.
Proper orientation is crucial for correct brake function. Ensure that the secondary shoe is the leading shoe (facing forward), and the primary shoe is the trailing shoe (facing rearward). Mixing up these positions can lead to improper braking and uneven wear.
Once the shoes are in place, reinstall the springs and pins. It is important to follow the correct orientation and tensioning procedures. The springs and pins must be seated properly to ensure the shoes remain in position during operation. Use a repair manual or take reference photos during disassembly to guide the reassembly process.
The self-adjusting hardware should also be reinstalled during this step. This hardware includes the adjustment screw assembly, tensioning springs, and any associated components. Apply a small amount of high-temperature grease to metal-on-metal contact surfaces and the adjuster mechanism to reduce friction and prevent seizing.
After installing the springs and self-adjusting hardware, the brake drum can be reinstalled. Slide the new or re-machined drum over the brake shoes and hub. If the drum does not fit easily, use the adjusting tool or screwdriver to turn the adjuster wheel, allowing the shoes to retract slightly. The goal is to achieve a snug fit without excessive resistance.
Once the drum is in place, reinstall the wheel and tire. Secure the lug nuts loosely at first, then torque them to the manufacturer's specifications once the vehicle is back on the ground.
Adjustment and Testing
After the brake shoes are installed, it is necessary to adjust them to ensure proper contact with the drum. With the wheel and tire reinstalled, spin the wheel slowly while adjusting the star wheel through the backing plate. The adjustment should be made until the brake shoes just make contact with the drum. There should be minimal resistance when the wheel is spun, indicating that the shoes are properly seated.
Once the adjustment is complete, perform a test drive to verify the functionality of the new brake shoes. Begin by pressing the brake pedal and checking for a firm feel. The pedal should have some initial travel but should not feel spongy or low. If the pedal feels low, further adjustment or bleeding of the brake system may be necessary.
During the test drive, apply the brakes lightly and monitor for any unusual noises or vibrations. These could indicate improper installation or misalignment of the brake components. Additionally, check for brake fluid leaks, which could point to issues with the wheel cylinder or other components.
After a few miles of driving, it is a good idea to lift the vehicle again and check the brake adjustment. The self-adjusting mechanism should continue to fine-tune the brake shoes as they are used, especially when the vehicle is driven in reverse. This mechanism ensures that the shoes remain in contact with the drum as they wear down over time.
Maintenance Tips and Common Mistakes to Avoid
Maintaining rear drum brake systems requires regular inspection and attention to detail. Here are some best practices and common mistakes to avoid during the installation and adjustment process:
Do not mix up primary and secondary brake shoes: As mentioned earlier, the orientation of the shoes is critical for proper brake function. Always verify the correct installation before proceeding.
Use reference photos or a repair manual: Drum brake systems can be complex, and components are often installed in a specific order. Taking photos during disassembly or consulting a repair manual can help prevent errors during reassembly.
Avoid over-tightening springs and adjusters: Over-tensioning can lead to binding and uneven brake performance. Adjust the shoes until they just make contact with the drum and avoid excessive resistance.
Replace worn or damaged components: If any parts such as springs, pins, or wheel cylinders show signs of wear or damage, replace them during the maintenance process. Reusing faulty components can compromise the effectiveness of the brake system.
Lubricate contact points: Apply anti-seize compound or brake grease to metal-on-metal contact points such as pivot points and adjusters. This helps prevent seizing and ensures smooth operation.
Check for leaks and contamination: Before completing the installation, inspect the system for any signs of brake fluid leaks or contamination. These issues can affect the performance and safety of the brakes.
Conclusion
Rear drum brake shoe replacement is a critical maintenance task that requires careful attention to detail. By following a systematic approach to disassembly, reassembly, and adjustment, users can ensure that their brake system operates safely and efficiently. The use of proper tools, reference materials, and best practices is essential for achieving a successful outcome. Whether performed by a DIY enthusiast or a professional technician, this process contributes to the overall reliability and performance of the vehicle’s braking system.