Understanding and Resolving Issues with Rear Brake Drums Why They Won't Go Back On

When it comes to vehicle maintenance, brake systems are critical for safety and performance. One common issue many car enthusiasts and DIY mechanics encounter is the difficulty of reinstalling rear brake drums after servicing. This article will explore the possible reasons why rear brake drums won't go back on and offer guidance on how to resolve the issue effectively.

Overview of the Brake System

Understanding how the brake system works is essential for troubleshooting issues. Rear brakes can either be drum or disc types, with drum brakes often found in older vehicles and some budget models. The drum brake system consists of several key components the brake drum, brake shoes, wheel cylinder, and parking brake mechanism. The brake shoes press against the inner surface of the drum to create friction, which in turn slows the vehicle down.

Common Reasons for Difficulty in Reinstalling Rear Brake Drums

1. Improper Adjustment of Brake Shoes One of the most common reasons for the inability to reinstall rear brake drums is that the brake shoes are improperly adjusted. When the brake system is serviced, the shoes may extend too far outward due to wear or misalignment. If the shoes are too far apart, the drum won’t fit over them. To remedy this, you need to adjust the brake shoes back to their proper position. This can usually be done by turning an adjustment wheel or using a screwdriver to manipulate the adjusting mechanism.

2. Residual Pressure in the Brake Lines After servicing the brakes, it’s possible that air or fluid is trapped in the system, causing residual pressure. This can push the brake shoes outward, preventing the drum from sliding back on. To alleviate this, you can loosen the brake line at the wheel cylinder slightly to release any trapped pressure or bleed the brake system to ensure that it’s free of air.

3. Incorrect Installation of Brake Components If any components were removed during the brake servicing—such as springs, retainers, or other hardware—they may have been improperly re-installed. Double-check that all components are correctly positioned and secured. If the springs are installed incorrectly, they may be holding the brake shoes in an extended position.

4. Corrosion and Dirt Buildup Brake drums can accumulate rust and grime, especially if the vehicle is older or used in harsh environments. This buildup can prevent the drum from fitting back on easily. Thoroughly cleaning both the brake drum and the shoes with a wire brush or brake cleaner can resolve this issue. Ensure the surfaces are smooth and free from imperfections before attempting to reinstall the drum.

5. Warped or Damaged Brake Drums Sometimes, the drum itself could be warped or damaged due to excessive heat or wear. A warped drum may not fit over the brake shoes properly. In this case, the best solution is to inspect the drum for warpage and either resurface it (if still within acceptable limits) or replace it entirely.

1. Check Adjustments Start by checking that the brake shoes are adequately adjusted. Turn the adjuster to retract the shoes.

2. Inspect and Clean Remove any debris and inspect the drum and shoes for damage. Clean all parts thoroughly.

3. Check Hardware Ensure all springs and components are correctly installed. If any parts seem worn or broken, replace them.

4. Reassemble Gently place the drum back over the shoes. Make sure it slides on smoothly. If it feels stuck, revisit the adjustments and cleanliness.

5. Test the Brakes After reinstalling the drum, pump the brake pedal a few times to ensure the shoes are properly seated and functioning.

Conclusion

While reinstalling rear brake drums can seem daunting, understanding the underlying issues and systematically troubleshooting them can make the process manageable. If challenges persist after following these steps, it may be prudent to consult with a professional mechanic to avoid further complications. Safety should always come first, and ensuring your brake system functions correctly is a vital part of vehicle maintenance.