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What are Disc Brakes?

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  • Written By: Sherry Holetzky
  • Edited By: Bronwyn Harris
  • Last Modified Date: 08 November 2016
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    2003-2016
    Conjecture Corporation
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Disc brakes, like any other style of brakes, are used to slow or stop movement. They work by applying friction and pressure that slows the movement of a wheel or stops it altogether. Also known as rotors, discs are attached to the wheels or in some cases are attached to the axle.

Disc brakes are generally made of ceramic materials or cast iron. They are powered in different ways, from electromagnetic, hydraulic, and pneumatic, to mechanical. When disc brakes are engaged, friction is created, causing the brake pads inside the brake calipers to push against the disc.

This causes movement to slow and can cause the wheel to stop moving entirely. These processes occur when you apply pressure to the brake pedal in your vehicle. While disc brakes have been used in vehicles from early on, they were not the most common type of brake systems. They were used mainly for sports cars or other high performance vehicles due to the heightened demand for stopping power in such vehicles.

Today, disc brakes are more common than drum brakes. They have also found uses in sporting equipment such as mountain bikes. Since there are various types of disc brakes, certain types work better for certain uses, equipment, or vehicles.

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For example, with racing or biking, slotted or drilled discs may be preferable as they allow air, dust, moisture, and gas to be released through openings in the disc. Otherwise, a film can form on the discs, which can create too much heat. This can lead to less than optimal performance as well as cracks and splits if the disc brakes have no form of ventilation.

When compared to drum brakes there are some important elements that make disc brakes the preferred option. Better heat resistance, a greater ability to recover after becoming wet, and the ability to apply proportionate force based on pressure applied to the brake pedal are key considerations. Still, in some light vehicles there may be a combination of disc brakes in the front and drum brakes in the back. Since front brakes tend to do most of the work, it makes sense that disc brakes are used in this location.

Utilizing both types of brakes allows manufacturers to keep costs down as well as helping create a simpler system for parking brakes. Weight must also be taken into consideration. Drum brakes add less to a vehicle’s overall weight than disc brakes do, so this combination can be quite effective depending on the type of vehicle.

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titans62
Post 4

@matthewc23 - If you look through the rim of your tire, you should be able to easily see whether you have disc brakes or drum brakes. They both look pretty similar at first glance, but there are a few ways to tell. If you've got hubcaps, though, it might be impossible to see the brakes without taking them off.

Disc brakes will usually look like a just a shiny, flat piece of steel a little less than an inch thick. Like the article said, these will almost always be on the front. On the back, to tell what kind you have, do the same thing. If they look like the front, you probably have disc brakes in both places. If

instead the back brake is a lot wider and kind of looks like it has grooves along the edges, that is a drum brake.

In my experience, most trucks, SUVs, and larger cars have two sets of disc brakes for added stopping power. Most regular sedans are a mix, though.

matthewc23
Post 3

How do you tell whether your car has disc brakes or drum brakes? Someone could tell me, and I would have no way of knowing if they were right or not.

I had to have my brakes repaired last year because something went wrong with the caliper on one of the tires, and the rotor had to be replaced as well. I guess that would mean I have disc brakes on at least one axle.

Are disc brakes usually more expensive to repair than drum brakes, or are they about the same? I know of a lot of people who change their own brake pads, so I'm sure it's not that hard, but I'm afraid to even jack up my car.

JimmyT
Post 2

@stl156 - Good questions. I think it is important for people to have a basic understanding of how a vehicle works so that they know what the mechanic is talking about. I have met a few people who try to use a bunch of technical terms just to make people think they need things that are really unrelated to the real problem.

Basically, a disc brake uses pads that push down on the rotor. The rotor is a round piece of metal connected to the axle and wheel. Drum brakes, on the other hand, sort of fit inside the rim of the tire. When you apply the brake, the drum expands and stops the tire that way. Disc brakes are more efficient because, when it rains, water can pool inside of drum brakes. Whenever the brake tries to work, the water can slow it down.

Like the article also mentions, disc brakes can be manufactured to better handle extreme conditions.

stl156
Post 1

Interesting article. I have always heard about disc brakes but I never really understood what they were. What is the main different between disc and drum brakes, though? Why would disc brakes be able to stop a vehicle faster when they were wet?

If a bicycle has disc brakes, I guess I can understand the basic concept of how they would work. I am guessing in a car, though, that the brakes are probably pneumatic considering that you have to have brake fluid to make them work.

I have also had to have my rotors replaced before when my brakes went bad. What role exactly do they have in the stopping process, and how do they get damaged when the brakes wear out?

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