All About Brake Pads and Discs

| November 2, 2012

replacing car brake padsLike a good friend, brakes should always be there when you need them. But unlike that good friend, brake pads and discs need occasional replacement. When that time comes, use the DexKnows listings to find an auto parts store where you can pick up quality replacements.

The disc brake system

Every modern vehicle has disc brakes on the front wheels and a growing number have them on all four. (Those that don’t use drum brakes at the rear.)

A disc brake has two main parts: a caliper holding two brake pads and a disc mounted behind each wheel. The caliper fits over the disc with a brake pad on each side. When the brake pedal is pressed, hydraulic fluid transfers that pressure to a piston in the caliper, pushing it out. As the piston moves out, it presses the pads against the disc. The harder the driver presses the pedal, the harder the pads grip the disc and the faster the car stops.


Any time surfaces rub together, heat is generated, and brakes are no exception. Although some pads used for racing cars need heat to make them grip, in your car, heat is a problem. Too much will damage both the pads and the discs and can even make the brake fluid boil. To prevent this, pads and discs are engineered for heat dissipation.


Pads are softer than the discs, so they wear out with use. How long they last depends on what kind of driving the car sees, but 25,000 to 50,000 miles is typical. Have the pads inspected at regular intervals and don’t forget that the discs wear out too, sometimes almost as fast as the pads.

Types of pads

A brake pad consists of friction material bonded to a steel backplate. What goes into the friction material is kept secret, but there are four main types: semimetallic, non-asbestos organic (sometimes called NAO), low metallic NAO and ceramic.

As the name implies, semimetallic pads contain metal. This takes heat away from the friction area and makes them durable, but they tend to wear out the disc and can be noisy.

NAO pads wear faster, though they are not as hard on the disc, and they create more dust. If you take pride in your wheels, these will have you spending more time cleaning.

Low metallic NAO pads are a compromise between the two. They last reasonably well but still wear out the disc.

Ceramic pads are expensive but provide good braking while being gentle on the disc. They tend to be used by performance enthusiasts.

What’s right for you?

It depends on your vehicle and the type of driving it sees. A heavier vehicle driven on steep hills would probably benefit from semimetallic pads, whereas a lightweight economy car driven mainly on flat roads will probably do just fine with NAO pads. Ask for a recommendation at the auto parts store or your auto dealer.

When to replace?

Any time you think you might have a brake problem, get them checked. Particular things to look for are:

Pad wear. Many pads have a wear indicator that squeals loudly as they get near the end of their life.

Pulsating brake pedal. This can mean that the discs have worn unevenly.

Pulling to one side. Your car or truck moves left or right when you brake.

Brakes are one component of your car that absolutely have to be there when you need them. A good auto parts store can tell you what you need. Find one on the DexKnows listings site.

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Category: Auto Parts, Auto Repair, Autos, Evergreen

About the Author ()

After twenty years in the automobile industry the craft of wordsmith called. Putting down the wrench, Nigel picked up a keyboard on which to express his passion for all things automotive.