Cars today generally use disc brakes. They have been around for many years, replacing the drum brakes used on the front wheels of most vehicles since about seventy to eighty percent of the stopping force is carried out by the front wheels. However, many vehicles today still use rear drum brakes. Rear drum brakes use friction produced by brake shoe pads when they rub against the rotating brake drum. It can slow down or stop the vehicle since the friction will convert the kinetic energy into thermal energy.
The rear drum brakes are often regarded as a “poverty spec” feature and are usually found on the base models of the auto manufacturer’s vehicle lineups. It is because the rear drum brakes are less expensive to install. Using a disc brake on a rear wheel needs a separate parking brake installed while with rear drum brakes, the parking brake can just be installed inside them. Rear drum brakes are built to last for a long time but they are also susceptible to wear and tear. You will know if they need replacements if you experience symptoms such as unusual brake pedal wear, scraping noises, or a loose parking brake.
Rear Drum Brakes: Do Rear Drum Brakes Do Anything?
Like mentioned earlier, about seventy to eighty percent of the vehicle’s stopping power comes from or is done by the front wheels and these front wheels generally use disc brakes. Many might have wondered, do rear drum brakes do anything? Why won’t car manufacturers use rear brake discs instead of rear drum brakes?
Although the front wheels with disc brakes are the ones that make most of the vehicle’s stopping power, you need to remember that all vehicles still need rear brakes to help them stop. For the people who are asking why rear drum brakes are still being used today instead of using disc brakes, like the ones used on the front wheels, you need to understand the following:
- Brake discs work efficiently and are already making most of the vehicle’s stopping power. If you add brake discs on your rear wheels, it won’t have that much effect
- Rear drum brakes are much cheaper and simpler to install. They also double as a parking brake. Using a disc brake on the rear wheel means that the auto manufacturer will have to install a separate brake for parking.
- Rear drum brakes are safer to use when the car is stationary or parked. Drum brakes can easily lock up the wheels and make better parking brakes. They do not rely on hydraulics to keep the car stationary. They just use the handbrake wire and some springs in the drum brake.
- Since rear drum brakes get lower stress, their drum brake shoes tend to last longer than the disc brake pads. Rear drum brakes are also in their sealed drum, which keeps them away from any potentially damaging materials. They don’t get wet, won’t need much regular service, and don’t get dirty. It means that it is cheaper to maintain.
- Rear drum brakes are smaller and lighter.
Although drum brakes are now being replaced by disc brakes, rear drum brakes are still found on many of the cars today. To better understand why it is still used on many cars today, we need to know the basics.
A drum brake consists of a number of components that work together. Its components include:
- Backing plate
This drum brake component is a metal-based band that is quite thin and is located on the back of the drum brake system. It is designed to protect the other drum brake components.
- Brake drum
Brake drums play an important role in the whole drum brake system. They are large metal disks made of aluminum or cast iron which are bolted to the hub of the wheels. A brake drum has a tough texture with a shape similar to a tube or drum. It rotates along with the hub, combining to create a frictional pair with drum brake shoes to slow down the car.
- Brake shoe
The brake shoe, which is also known as a brake pad, is a curved piece of metal positioned on the rear wheel. It is used to put the brake on a drum brake system. It has friction material inside the brake lining that pushes against the brake drum that makes the car decelerate or stop.
- Wheel cylinder
The wheel cylinder of a drum brake system has several parts such as the housing, bleeder nut, spring, and the piston. The piston moves outwards whenever the driver steps on the brakes. A force is created when the piston pushes the brake shoe outwards and this makes the car slow down or stop. If the wheel cylinder becomes damaged or fails to work, it can affect the performance of the drum brakes.
- Return spring
The return spring or the retracting spring comes to action when you take your foot off the brake pedal. It is the one that pulls the brake shoes away from the drum’s friction surface. It returns the brake shoe to its original position.
- Brake shoe adjuster
The function of the brake shoe adjuster is to adjust or maintain the minimum gap between the drum surface and the brake shoe to prevent them from touching each other.
The master cylinder will compress its fluid whenever you depress the brake pedal. The wheel cylinder’s piston will then expand outwards and this outward movement will force the brake shoe to press on the brake drum. When the brake shoe lining comes in contact with the inner surface of the drum, the wheel’s movement will decelerate and stop the car. The return or retracting springs will then pull the brake shoe inward when you take your foot off the brake pedal. This will then remove the contact between the drum brake lining and the brake shoe. This is how the rear drum brakes work.
Rear Drum Brakes: How Do You Know If Your Rear Drum Brakes are Going Bad?
It is said that rear drum brakes do not need that much service and they can last for a long while, but just like any other components of the car, it does not last forever. Rear drum brakes are also susceptible to wear and tear. How will you know if your rear drum brakes are failing? You may know it when you experience any of the following symptoms:
- Unusual or inconsistent brake pedal feel.
Inconsistent brake pedal feel is one of the first symptoms you may encounter when your rear drum brakes are faulty. You may feel unusual vibrations under braking. This can happen when the brake shoes become too worn and they can no longer press against the drum firmly. Worn drums can also cause shuddering or pulsating feels when you step on the brake pedal.
- Loose hand brake or parking brake.
If you notice that your hand brake or parking brake is loose, it might be an indication that your rear drum brakes are failing. You may need to yank your hand brake really hard to keep your car from moving. When this happens, you might need to replace your brake shoes since they are no longer capable of squeezing against the inside of the drum.
Replacing the brake shoes is necessary since your hand brake may not work as efficiently as it should. You may notice your car move an inch or two on a steep incline after engaging the parking brake. Since this problem can also be caused by a loose hand brake cable, it is best that you have your car checked by a mechanic to determine what causes it.
- Scraping noises.
When you hear scraping noises whenever you step on the brake pedal, it might be caused by bad rear drum brakes. Excessively worn brake drums and brake shoes may give off unusual sounds such as metallic scraping or scratching noises. If the problem becomes too severe, you might need to have the drum machined or replace it all at once.
If you experience any of these symptoms, it is best that you have your car checked by a professional. If your car needs a rear drum brake replacement, the average cost for it is between $200 and $399. The cost can vary depending on the type of vehicle you have and the auto repair shop you choose.
Rear Drum Brakes: How Often Should You Change Rear Drum Brakes?
Rear drum brakes usually last for around 150,000 to 200,000 miles under normal conditions. After that, the braking friction tends to cause the drum brakes’ inside diameter to increase and affect the contact with the brake shoes. The brake shoes can last for about 40,000 miles before wearing out and calls for a replacement.
To ensure that your rear drum brakes will last for a long time, you need to check the following:
- Brake fluid
You need to check your brake regularly and make sure that an adequate amount of brake fluid is maintained. This can help your rear drum brakes to last longer since the brake fluid is known as the conduit for most of your braking system’s processes. If the right amount of brake fluid is not maintained, your brakes won’t be able to create the needed hydraulic pressure and braking power to stop your car. Aside from maintaining the right amount of brake fluid, you also need to make sure that it is not contaminated.
Leaks on your system can also cause your rear drum brakes to become faulty. If your car has leaks, have it checked and repaired immediately. You need to look out for leaks in your brake fluid reservoir, wheel cylinders, master cylinders, brake lines, or brake hoses.
- Friction material
The brake shoe has a friction material that can wear out over time. You need to check it regularly since a worn out shoe can affect the performance or effectiveness of the drum brake. If it needs a brake shoe replacement, you need to have it done right away. Do not wait until a bad brake shoe starts to rub against the metal drum before you have it replaced.
Seals or rubber rings help stop the hydraulic brake fluid from leaking out of the caliper as well as keep the brake fluid from having moisture and getting contaminated. If the seals become bad and fail to do its task, your brake fluid can get contaminated or can leak. As mentioned earlier, this can cause your rear drum brakes to become faulty.
- Dust boots
Dust boots are designed and built to keep dirt and other contaminants from reaching into the caliper piston. It is an important part since the brake components in your car are always exposed to brake dust and other road debris. If the dust boots become bad and fail to do their job, it can result in a stuck brake pistons. When this happens, your rear drum brakes will wear out and fail to operate properly.
It is the brake hose’s job to carry the brake fluid from the brake line to the wheel’s brake caliper. The brake hoses are always exposed to pressure and flex which lets the wheel cylinders and calipers move up and down. This constant exposure to pressure and flex causes the hoses to wear out over time. Cracks or tears can develop over time and it can weaken the hose which can compromise its ability to hold pressure and can leak. Make it a habit to check your hoses and other components regularly. If they need replacing, have them replaced immediately since it can help prolong the life of your rear drum brakes.
Rear drum brakes play an important role in keeping you and your car safe. It is crucial to the overall performance and proper operation of your car’s braking system. If you experience any signs of a bad or failing rear drum brakes, you need to have your car’s whole brake system checked by a mechanic to diagnose and correct the problem. Problems with the car’s braking system should never be ignored since it is its most important safety system.