Drum vs Disc Brakes
Brakes are the main stopping force for your vehicle outside of engine braking and scraping up against the occasional curb or barrier. Most brakes come in two forms, disc and drum form factors, each coming with their own benefits and shortcomings which will be covered in this article.
Drum brakes were the most common form of brake up until around the 70’s when the switch to disk brakes was made on most commercial cars after race cars had been using them for decades already. Drum brakes consist of an outer “drum” or housing that rotates with the wheel and as braking pressure is applied, a set of pads expands on the inside of the drum to create friction on the inside of the drum to create friction and eventually stop the car.
Drum brakes have some unique benefits including cleaner operation, cheaper cost and maintenance overall. The unique and simple all in one design keep manufacturing costs down while still providing adequate performance. Replacing individual components is easy as most of the components in the drum are held in place by just a tensioner spring. There is also no need to wrestle with depressing the pistons of the caliper on a disc brake during a brake job. The enclosed design also keeps brake dust from decorating your wheels when braking. Another small benefit is the ability to incorporate the parking brake into the drum brake assembly. This further helps keep assembly and other general costs down which is the main reason this form factor is so popular. The major downfall to drum brakes is their inability to dissipate heat which leads to brake fade which is never a great situation to be in. As the drums use friction to stop your vehicle like any brake, heat is also created, having lots of heat build up inside of a metal drum brake basically turns it into an oven which creates the ideal environment for brake fade. As the drum heats up from more and more braking over time, stopping power will eventually fade from the inability for the drums to properly dissipate heat. Some modern passenger and sedan vehicles today come equipped with drum brakes but only a set in the rear in most cases. This is because disk brakes have superior braking power and are placed of front where most of the weight transfer ends up during braking and also why your front brakes tend to wear faster than the rears. This allows manufacturers to save on costs by using drum brakes in the rear since stopping power comes mostly from the front and the drums are supplemental.
Disc brakes prove to be a significant leap in brake technology from the drum brake. Using a spinning disc covered on one portion by a caliper that bites down with two brake pads on each side of the disc to create friction and slow your car. Since the rotor is exposed the heat created from braking is able to dissipate faster than a drum brake. This open design allows the rotors to cool down quicker than a drum, in turn holding off brake fade for much longer. As a small bonus, after heavy and frequent braking disc rotors begin to glow red hot. Not great for performance but it looks damn cool.
These open rotors also provide for easy inspection of your braking system. You can get an idea of how much life your pads have left and can also visually inspect your rotor without having to take your wheel and drum cover off to inspect drum brakes. The heat dissipation properties of disk brakes alone make them a clear choice for performance applications where braking is frequent and heavy. Also in wet conditions disk brakes are able to fling water and debris off of the rotor as opposed to drum brakes where things have the chance to stay inside the drum and either dull your braking effect or cause damage. Disk brakes also come in a variety of configurations to better suit your braking needs and application with specially surfaced rotors that provide increases in braking performance and heat dissipation. The improved cooling design and braking mechanism in disc brakes allow a racer to carry more speed deeper into a corner and brake harder, in turn helping to reducing lap times. Braking force is determined by the overall size and surface area that the brake pads come in contact with along with how hard the “bite” of the brakes is. These forces are applied by pistons in the brake caliper that press the brake pads onto the brakes to begin slowing you down. “Big brake” kits commonly come with over 4 pistons in a caliper to provide immense braking force. A downside to all of these cooling and stopping benefits is brake dust. The open design of the calipers means your tires get coated in a thick black coat of brake dust which makes cleaning multi spoke wheels a blast. From sheer performance numbers alone disc brakes win hands down. But cost efficiency and repairability still keep drum brakes in contention with today’s disc systems. Each has their pros and cons and both will be around for a long time to come. Keep in mind your braking isn’t just affected by your brake setup. Your tires play a huge part in translating that stopping power to the ground and your overall suspension tune.