Replacing the drum brakes on your car or truck is a great way to get started in the world of automotive DIY.
Why drum brakes?
The drum brake has been around pretty much since cars were invented, and they continue to be used (albeit not as much) because they're cheaper to produce than disc brakes. This is partly because there are fewer compionents involved in a drum brake, and the parking brake can be located inside the drum. A rear disc parking brake entails the use of many more parts.
Drum brake advantages
Brake shoes today are still being used. Here are some advantages that drum brakes have over disc brakes:
- Drum brakes can provide more braking force than an equal diameter disc brake.
- Drum brakes last longer because drum brakes have increased friction contact area than a disc.
- Drum brakes are cheaper to manufacture than disc brakes.
- Rear drum brakes generate lower heat.
- Wheel cylinders are simpler to recondition than with disc brake calipers.
- Brake shoes can be remanufactured for future use.
- Drums have slightly lower frequency of maintenance due to better corrosion resistance.
Drum brake disadvantages
- Excessive heating can happen due to heavy braking, which then can cause the drum to distort, and thus cause vibration under braking.
- Under hard braking, the diameter of the drum increases slightly due to thermal expansion, the driver must press the brake pedal farther.
- Brake shoes can overheat to the point where they become glazed.
- Excessive brake drum heating can cause the brake fluid to vapourise.
- Grab is the opposite of fade: when the pad friction goes up, the self-assisting nature of the brakes causes application force to go up. If the pad friction is enough, the brake will stay engaged due to self-application, even when the external application force is released.
- Another disadvantage of drum brakes is their relative complexity.
- Maintenance of drum brakes is more time-consuming, compared to disc brakes.
Brake hardware
Drum brake hardware plays an important role in controlling noise and allowing the new brakes to stop quietly and efficiently. It is highly recommended that the vehicle’s drum brake hardware be changed along with every brake maintenance.
- Many people are tempted to reuse the old hardware even if new hardware is included in the box. This should be avoided; instead, use brand new hardware every time.
- Drum return springs that pull the shoes back away from the drums when the brakes are released, may be worn, stretched or broken. This causes the brakes to drag.
- The hold-down springs that hold the shoes against the backing plates may be corroded. If they break, the debris can jam itself between the shoes and drum causing the brake to drag or bind.
- Drum brakes as the shoes wear, brake pedal travel would increase were it not for the adjusters. The adjusters, however, are susceptible to corrosion and sticking.
- Adjuster springs, help maintain tension on the adjusters, but lack of its use can allow cables to corrode and stick in place, preventing the parking brake from applying or releasing.
- A special high-temperature brake lubricant should be used on the drum brake.