Daniel Susco
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Drums Vs Discs: How Your Brakes Work And Are Picked

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Almost all new vehicles use disc brakes, but a few (looking at you, Toyota Tacoma) still include drum brakes, and drum brakes used to be the norm. So, I wondered, what is the difference, and why are we mostly using discs now?

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Drum brake pads

Drum brake pads

How they work

Both drum and disc brakes work by pushing pads against something to create friction and slow the wheels, but the way that they do it is different.

In drum brakes, the brake shoes are inside a round metal cylinder, called the drum. When you step on the brake pedal, the shoes push outward, rubbing against the cylinder to make friction and slow down the wheel.

In disc brakes, rather than pushing out against a piece of metal, the pads push in against a disc. The clamping motion generates friction and slows the wheel.

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Drums or discs?

So, the choice between drums and discs rests on three things: cost and performance. Cost is easy, and leans in the drum brake system’s favor, because it is cheaper to produce.

However, performance is a little more complicated. For example, drum brakes are far more likely to experience brake fade. This happens when you lost braking power because the pad and what it is rubbing against aren’t making enough friction to slow you down, usually because the brake pad is too hot. In drum brakes, the pad is inside the drum, so doesn’t dissipate heat that well. On top of that, as the pad heats up, the drum does, too, and expands. As a result, the pad has to move farther just to make contact. Meanwhile, with their open-air design, disc brakes easily cool during use. As a result, disc brakes are far better in performance.

So, if the automaker wants to save money, they will often put a set of disc brakes on the front wheels, and drums on the rear wheels. That way, they get the better performance of the discs and cost savings of the drums.

News Sources: HowStuffWorks, NAPA, EBC Brakes