Brakes

Everything you need to know about brakes in one sentence: Get them checked regularly. What’s below is just icing on the cake—but it might save you some money.

Brakes generally are hard working and undemanding. You don’t need to know a whole lot about them—the only thing you really need to know is that they should be inspected regularly. But a little more knowledge can be a helpful thing. Here is a brief description of how a car’s brakes work and what you can do to keep them happy.

There are two types of auto brakes: disc and drum. Many cars have both, with discs commonly on the front wheels and drums on the rear.

Drum brakes. The drum is an iron casting shaped much like a frying pan without the handle. It’s bolted to the wheel and spins with the wheel. Inside are two curved brake shoes fastened to a backing plate that doesn’t turn with the wheel. Drum brakes work when the brake shoes are forced against the inside walls of the spinning drum. The resulting friction slows the wheel.

Disc brakes. Instead of a drum, disc brakes have an iron disc, or rotor, that rotates with the wheel. A caliper, which does not rotate, holds brake pads on either side of the disc. The caliper operates like a vise. When you step on the brake pedal, the caliper closes, pressing pads against the rotating disc. Friction slows the wheel.

Between your foot and the brake. Stepping on the brake pedal activates a hydraulic system in which fluid transmits foot pressure (in the case of power brakes, with a boost from the car) to all four brakes.

This is accomplished by a master cylinder that translates brake pedal motion into hydraulic pressure. It transmits this pressure through brake fluid piped to a cylinder (drum brakes) or caliper (disc brakes) at each wheel.

The brake cylinders or calipers receive the pressure and translate it back into motion—moving brake pads to contact the rotor or shoes to contact the drum.

Emergency/parking brake. This usually is not a separate braking system. It’s a manual way of setting brakes, bypassing the hydraulic system. Most often it operates only on the rear wheels.

The parking brake pedal or lever is attached to a wire cable. The cable’s other end is attached to the brakes and sets them when pulled.

How to tell when you need brake work. Brakes don’t necessarily give you helpful hints when they need attention. It’s important to have them inspected periodically; use the schedule in your vehicle’s owner manual. A rule of thumb might be to get an inspection every third oil change—every 9,000 miles. Or have them inspected every 6,000 to 9,000 miles when you have the tires rotated. Don’t change oil that often? Don’t rotate tires? We’re not judgmental, but at least get your car’s brakes inspected every year.

Even reticent modern brakes might give you a hint something is wrong before it becomes catastrophic. Symptoms worth looking into include low pedal, pulling, grabbing, any new noises (grinding or squealing are cries for help), or any change in brake feel. Failure to stop in a reasonable distance is a decent indicator, too.

Shoes and pads used to be made of asbestos; now they’re composed of a wide variety of synthetic materials, such as high-tech plastics and fibers in various mixes. They tend to lead shorter lives in these asbestos-free days. Even so, how long shoes and pads last depends largely on how you drive: A heavy foot shortens their life.

The brake job. If a brake inspection shows you need "a brake job," it commonly would include:

  • replacing shoes and pads
  • flushing and bleeding the hydraulic system
  • resurfacing drums and rotors
  • cleaning and lubricating hardware as needed.

Sometimes a high-mileage vehicle or one that has been driven under harsh conditions or in a particularly aggressive way needs more help. In this case, a "major" brake job could include:

  • replacing shoes and pads
  • replacing hoses
  • resurfacing drums and rotors
  • rebuilding calipers and wheel cylinders
  • replacing master cylinder
  • replacing springs and other hardware as required
  • flushing the hydraulic system and replacing the brake fluid.

Brake work is not on the now extremely short list of auto maintenance jobs that can be done by shade-tree mechanics. Find a reliable repair facility when your car needs brake work.

This article was first published in November 1999. Some facts may have aged gracelessly. Please call ahead to verify information.

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