What do rear drum brakes do

When the brakes are applied, only the caliper pistons move, pressing the brake pads against the disc. When they are used it is only on the rear axle. Instead of a caliper that clamps brake pads against a rotor, a drum brake system has a wheel cylinder with pistons that push brake shoes out against the inside of a spinning drum. This contact slows and stops the rotation of the brake drum and the wheel.

Although they both operate with the same basic hydraulics, the two types of brakes perform differently. Disc brakes are more efficient, provide better stopping power, dissipate heat easier and work better in wet conditions, all while being less complex. Some base models have disc on the front axle and drum on the rear, to keep costs down.

In these models, why are disc put on the front and drum on the rear? A typical, unloaded vehicle is already about 10 percent heavier in front due to the engine.

Then when you hit the brakes, the weight of the car transfers to the front. More braking power is needed there, making it a job for disc brakes. Stopping power. Disc brakes apply more braking force faster, resulting in shorter stopping distances. Heat management. Since they are exposed to air, disc brakes cool better.

This can cause brake fade, a loss of stopping power when friction material overheats. Wet performance. Disc brakes perform better in wet conditions because they are open to the air and can sling water off easily. Plus, the rotors get dried by the pads dragging across them. When water gets inside a drum brake it tends to get trapped inside the drum, so it takes longer for the friction material to dry out. Emergency brake. This feature is easier to install on a drum brake than to a caliper or inside the hub of a disc brake rotor.

Disc brakes are self-cleaning. Drum brakes are closed and are prone to brake dust collecting from the shoes, so they need periodic cleaning. Drum brakes have more hardware and can be more complex to service. But drum brake shoes and wheel cylinders typically cost less to replace than disc brake pads and calipers. Since a lot of heat is generated by the braking system, plenty can go wrong.

The act of braking converts kinetic moving energy of the vehicle into thermal energy heat , subjecting many parts to very high temperatures. This means a lot of wear and tear even in normal conditions. Some brake components will need to be replaced over the life of a vehicle.

The solution is simply to get regular checks and replace pads, shoes and other components before braking is compromised or other parts get damaged. Disc brake pads slow the rotor through friction and they wear with normal use.

Eventually, they become too thin to function properly. Same thing for drum brake shoes. The friction material on the shoe gets worn out and braking is compromised. These components should be inspected regularly. Skip to main content. Australia Australia New Zealand.

Technical Bulletins Dec. How do drum brakes work? How to tell if your brake shoes need changing? Inconsistent brake pedal feel. If the rear brakes are drum brakes, the driver may feel vibrations under braking.

The initial bite when the brakes are still cold may be lacking. This is because the brake shoes are so worn that they cannot firmly press against the drum. Hand brake feels loose.

If the hand brake requires a hard yank to keep the car from rolling off, chances are the brake shoes need replacing. On a steep incline, if the car moves an inch or so before coming to a rest, the drum or brake shoes would need to be inspected. Why drum brakes? 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. Drum brakes have a built-in self energizing effect that requires less input force such as hydraulic pressure 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 vaporise. 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.