Understanding the difference between drum brakes and disc brakes

Drum brakes and disc brakes are critical for slowing down your car, but they work in different ways. In this article, we'll explain the difference between drum brakes and disc brakes, discuss their advantages and disadvantages, and provide some basic advice on maintenance and upkeep.

When you depress the brake pedal, hydraulic pressure is generated in the master cylinder, which pushes brake fluid to the pistons that operate your brakes. The pressure applied through the braking system pushes friction material against a rotating surface (the bowl of a drum brake or a brake calliper).

Cars can be fitted with drum brakes, disc brakes or a combination of the two (typically disc brakes at the front and drum brakes at the rear).

It's easy to see whether your car has drum or disc brakes. If you can see a shiny metal disc with a calliper, then you have disc brakes. If you see a bowl-shaped, often rust coloured as it is made of iron, object behind the wheel, then you have drum brakes/.

The drum braking system has five parts: hydraulic wheel cylinders, curved brake shoes, return springs, a backing plate and the brake drum.

When you push the brake pedal, brake fluid is pushed through the hydraulic system which activates the pistons in the wheel cylinders. This moves the curved brake shoes outwards and into contact with the drum. The friction generated when the shoes meet the rotating brake drum converts kinetic energy into thermal energy and slows you down. Once the pressure on the brake pedal is removed, the return spring inside the brake drum pulls the shoe away from the surface.

Drum brakes offer greater stopping ability than disc brakes, however they are prone to overheating. This can reduce the efficiency of the braking material and in rare cases, lead to distortion of the brake drum. It can also cause to the brake fluid to overheat leading to brake fade. A drum braking system also has more moving parts, which may require more maintenance.

Disc braking systems have a rotating disc (sometimes referred to as a rotor), a calliper and brake pads. When you push on the brake pedal, pistons inside the brake calliper push the pads against the rotor, again, converting kinetic energy into thermal energy, slowing you down.

Disc brakes are a simple – and effective system. The larger the size of the brake disc, the more effective it is at dealing with and dissipating the heat generated while braking, preventing overheating and brake fade. The brakes are less likely to grab or slip, even in extreme weather conditions. The system's simplicity means it's cheaper to work on, often enabling amateur mechanics the ability to replace consumables like brake discs and pads at home with a few standard tools.

Disc braking systems can be more expensive to manufacture and maintain than drum braking systems. The increased efficiency comes at the cost of operating time, with brake pads and brake discs needing to be replaced more frequently than similar drum brake components. Take care though as brake discs can become warped when they are continually exposed to high temperatures caused by excessive braking.

Ultimately, drum brakes and disc brakes are both safe and effective ways to stop your vehicle.

You're most likely to find drum brakes fitted front and rear on older cars and commercial vehicles. Manufacturers often fit cars with disc brakes at the front and drum brakes at the rear. This is because most (70-80%) of vehicle braking happens at the front, so it makes sense to fit disc brakes where they’re most effective.

Both braking systems will provide years of stress-free driving as long as they’re maintained. Some of the signs your drum brakes or disc brakes may need some attention is noise coming from the braking system, longer stopping distances, or feeling like you need to push harder on the pedal to brake. If you experience any of these, it's time to get your braking system checked out.

It doesn't matter if your car has disc brakes or drum brakes; you can find all the replacement brake parts you need at Halfords. Type in your car's registration plate, and you'll see all the brake parts, including discs, rotors and pads, that will fit your vehicle.

You can also book a free brake check. Our expert technicians will perform a 6-point check covering your entire braking system. They'll provide impartial advice on any problems and a price to fix them – book online today.