Most luxury cars on the market today contain a combination of disc and drum brakes. Front wheels always possess disc brakes, while drum brakes are often used on rear wheels. Yet many car owners fail to understand the distinction between these two methods of braking — often to their own detriment.

Learning more about how automotive brakes work will help ensure that your brakes do not develop costly and potentially dangerous problems. This article will increase your knowledge of the different ways in which disc and drum brakes work.



Drum Brakes

Drum brakes are the logical place to begin, since they represent the oldest style of automotive brake. As its name implies, a drum brake consists of a circular drum attached to the inner face of the wheel. As the wheel rotates, so does the drum. Inside of the drum reside a set of so-called drum shoes.

Depressing the brake pedal causes the shoes to press outward, coming into contact with the inside wall of the drum. This, in turn, generates the friction necessary to slow the vehicle. While quite effective under most circumstances, drum brakes possess one key flaw which nowadays keeps them from being implemented on all four wheels of a car.


The problem has to do with the amount of heat generated during braking. When stopping on relatively level roads, drum brakes exhibit no real problems. But when braking under more intensive conditions — for instance, when going down a steep hill — things start to get a little overheated.

This leads to the unwelcome phenomenon known as brake fade. Essentially, the hotter the brakes get, the less effective their stopping power. Because drum brakes proved unreliable at the times they were most needed, they are now only used on rear wheels, which bear a much lower proportion of the stopping responsibility.


Disc Brakes

Disc brakes utilize similar principles when it comes to stopping. In other words, they harness the power of friction to bring a vehicle to a stop. They also generate heat in the process. Unlike drum brakes, however, disc brakes have a much easier time dispersing this heat. This stems directly from the superior design of disc brakes.


As noted above, a drum brake houses its components inside of a sealed metal drum. This allows heat to build up much more easily. A disc brake system, by comparison, remains exposed to open air during its operation. Stopping is accomplished through the action of a brake caliper, to which a brake pad is mounted.

When you press down on the brakes of your car, the flow of brake fluid causes the caliper to contract around the circular rotor. The rotor connects directly to the wheel. As the brake pad tightens around the rotor, the wheel loses its momentum. Being exposed to the air around the wheel, a disc brake rotor has a much easier time dispelling heat — even when going down the steepest of hills.


Today's Cars

This fact leads many people to wonder why drum brakes continue to be implemented at all. The answer, in most cases, has to do with economics. Simply put, drum brakes remain less expensive to manufacture. Thus, while high-performance, high-cost cars often boast four disc brakes, most models stick with drum brakes on the rear wheels.


Because your rear brakes will never be responsible for more than 40% of your car's stopping power, those drum brakes will never be put in a position to cause problems. Of course, no brake will continue to work as intended unless you keep it properly maintained. For more information on keeping your brakes primed for service, please don't hesitate to call the pros at British 4x4 Luxury Auto Repair.