Like any other technology over the pats few decades, brake mechanics have continued to improve. Through the introduction of components such as lightweight steel and carbon fiber, vehicles have become safer and stopping distances reduced. The early 1970’s saw the first major improvements in brake technology with the introduction of disc brakes. Initially only the front wheels were fixed with the discs as that is where the majority of a car’s stopping power lies. The rear wheels continued to have the traditional drum brakes. If you don’t know the difference don’t worry, that will be explained shortly!
Most cars these days generally have all four wheels fitted with disc brakes, though in some cases manufacturers revert to the old setup of having drum brakes in the rear. This cuts both the production price and the cost to consumers. It is generally agreed though that disc brakes perform better than the older drum version, but why is this?
Heat and Friction
In order to understand the difference between disc and drum brakes it’s important to know a few basic principles about how each functions, namely heat and friction. When you press down the brake pedal of your car, resistance is applied to the moving wheels and friction and consequently heat are generated. The difference between disc and drum brakes rests in the speed and efficiency with which the brake system slows the wheel through friction and eliminates the heat that is consequently generated. Let’s take a look at how each version does that.
Traditional Drum Brakes
Drum brakes take their name from the fact that the brake components are housed within a cylindrical drum. Inside is a set of shoes that are forced against the wheel when the brake pedal is pressed, thus slowing the wheel. The brake shoes are composed of a heat-resistant material and brake fluid transfers the movement of the brake pedal to the brake shoes. Though quite efficient, the drum system contained a major flaw; when descending a steep hill or constantly slowing down while traveling at high speeds, the brakes would often lose effectiveness as they became unable to process the heat generated by the friction of the drum shoes against the wheel.
Modern Disc Brakes
The design of modern disc brakes eliminated the flaw in the drum version. Rather than having just brake shoes, they also contain brake pads, which clamp together when the brake pedal is pressed down, engaging a rotor which constantly cools the brake shoes by drawing in air. This eliminates overheating and allows the brakes to function consistently, even when braking on a steep downhill slope while carrying a heavy load.
Most vehicles today employ both systems; the disc in front and the drums in the rear wheels. This system is completely safe and capable for the majority of modern cars. Because most of the stopping power is contained in the front wheels, the disc brakes are placed there. A well-designed drum system is more than adequate for the rear wheels.