Drum Brakes vs Disc Brakes

Drum Brakes vs Disc Brakes

Last Updated July 23, 2020 | Alison Smith

Close up of the inside of a drum brake showing the springs, piston, and spindle

Since the 1900s, auto manufacturers had primarily used drum brakes on their vehicles. It wasn’t until the early 1970s that automakers began switching to disc brakes.

Although there are differences between drum and disc brakes, they function the same. While wheels use kinetic energy when in motion, brakes use friction to create heat energy. Once all the kinetic energy is transferred to heat energy, your car comes to a stop.

Even though they do the same thing, disc brakes outperform drum brakes in several ways. But there are a few reasons why drum brakes are still in use today.

What Are Drum Brakes?

Drum brakes have a brake cylinder, pistons, brake shoes, an adjuster, and springs contained in a round drum. They’re commonly seen on older vehicles, although many modern cars still have rear drum brakes. Since the front brakes provide most of the stopping power, many automakers opt for drums in the rear to cut costs.

When it comes to restoring a classic car, some people choose to keep the drum brakes to maintain authenticity. Others go the restomod route by replacing the outdated front drum brakes with disc brakes.

How Do Drum Brakes Work?

When you hit the brake pedal, a plunger in the master cylinder pumps fluid into the brake cylinder. The fluid expands the pistons in the cylinder outward, forcing the shoes to rub against the brake drum lining. This generates the friction needed to slow your car to a stop.

Springs sit between the two pistons and the shoes so all the parts return to the correct spot when you release the brake pedal. As the shoes wear down, the adjuster unwinds so the distance between the shoes and the drum surface is always the same.

GIF illustrating how a drum brake works

Close up of a disc brake opening

What Are Disc Brakes?

Beginning in the mid-1950s, disc brakes became a popular alternative to drum brakes for performance vehicles. A few decades later, front disc brakes started to become standard on most cars. Many modern vehicles also use disc brakes in the rear as well.

Disc brakes use a thin metal rotor, a brake caliper, and two brake pads that spin along with the wheel. Compared to drum brakes, disc brakes are lighter and take up less space. They’re also exposed to outside air, which allows them to quickly dispel heat.

How Do Disc Brakes Work?

When pressing the brake pedal, the master cylinder sends fluid through the brake lines to the caliper. The pistons in the caliper then squeeze the brake pads onto the rotor to create friction and stop the wheel from spinning.

Rotors can be solid or vented. Solid rotors are good for everyday driving applications and can often stop quicker as they have a larger surface area. Drilled or slotted rotors will dissipate heat faster since they let more air through. This makes them better for performance driving as they will experience less brake fade due to heat buildup. Vented rotors will also be noisier and can wear out quicker, which is why racers often switch them out after every race.

GIF illustrating how a disc brake works

Drum and Disc Brake Head-to-Head

Both drum and disc brakes use friction and heat to slow your vehicle down. While they may serve the same function, there are some areas where one outperforms the other.

Heat Buildup & Brake Fade

When it comes to dissipating heat, disc brakes are the clear winner. If you’re driving down a steep hill or braking repeatedly, drum brakes can quickly overheat. The enclosed design of a drum brake traps the heat inside causing brake fade. Since brakes only function properly when absorbing heat from the moving wheels, brake fade decreases stopping power. That’s not something you want when racing or going downhill.

Disc brakes are less prone to brake fade and overheating due to their open-air construction. Vented rotors allow disc brakes to dispel heat even faster, which is important if you do any type of racing. That’s why converting from drum brakes to disc brakes is a popular modification in performance vehicles.

Although performance drivers may install disc brakes in both the front and rear, it’s more common to upgrade just the front brakes. The main thing the rear brakes do is keep the vehicle from swaying side to side when you’re braking. Drum brakes can handle that job very well.

Winner: Disc Brakes

Wet Weather Conditions

Heat may be the number one enemy of a car’s braking system, but water isn’t too far behind. The drum brake’s closed-off design that traps heat also makes it difficult for water to escape. When driving through a puddle or a heavy rainstorm, water can collect in the drum brake and reduce braking performance.

The open-air design of disc brakes makes it easier to dispel water. Because they dry quicker, disc brakes perform better than drum brakes in wet conditions.

Winner: Disc Brakes

Brake Inspections

Because disc brakes aren’t enclosed like drum brakes, they’re much easier to inspect. When it comes time for you or a mechanic to check the brakes, the wheels can stay on while they’re inspected. You would have to remove the wheel to inspect drum brakes.

Winner: Disc Brakes

Maintenance

When it comes to maintenance, drum brakes are going to be more time-consuming due to their complexity. They have more hardware than disc brakes. Disc brakes are also self-cleaning, where drum brakes need to be cleaned periodically. The good news is that it’s often cheaper to replace parts for drum brakes.

Winner: Disc Brakes

Affordability

Disc brakes are often more expensive than drum brake setups. Due to their affordability, many auto manufacturers opt to use them in the rear of a vehicle to save money. For car owners, they’re also cheaper to replace.

Winner: Drum Brakes

Appearance

Close up of a black wheel and disc brake on a Mustang

When it comes to appearance, drum brakes can’t compare to disc brakes. The open-air design of disc brakes makes them easily seen through the wheels. Some wheel styles are even made so you can show off the brakes better.

Painting calipers is a popular option, but the safest way to customize your disc brakes is through caliper covers. They come in a variety of colors and designs so you can give your car a custom look. Drum brakes get the job done, but they’re not aesthetically pleasing.

Winner: Disc Brakes

Which Is Better, Drum or Disc Brakes?

Because disc brakes offer superior performance, many choose to convert their drum brakes to a modern disc brake setup. If you’ve got drum brakes in both the front and rear, upgrading to front disc brakes can boost braking power. Front disc brakes offer plenty of braking power for the average driver. You probably won’t need disc brakes in the rear unless you plan on racing the vehicle or hauling heavy loads.

If you’re working on restoring a classic vehicle, you may want to stick with the factory drum brakes for a more genuine restoration. Drum brakes will still offer good braking performance, but they aren’t as reliable in wet conditions and are more prone to brake fade. As long as you aren’t repeatedly braking, drum brakes are sufficient and will cost less than disc brakes.

Sources: Edmunds, How Stuff Works, Car Throttle, Haynes

Drum Brakes vs Disc Brakes

Although vehicles have used drum brakes since the early 20th century, they still remain relevant today. Since the 1970s, disc brakes have slowly taken the place of the drum brake. Even though disc brakes offer better performance, there are still reasons why drum brakes are used in modern vehicles.

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