A drum brake on a car. An auxiliary brake is really a fancy way of saying a parking brake. Here's everything you need to know about how auxiliary brakes work.

What Is an Auxiliary Brake?

What is an auxiliary brake? More commonly known as a “parking brake,” this piece of equipment serves more than one important function on your automobile. And yet, in our age where automatic transmissions are far more common than a clutch pedal, this particular brake is sometimes overlooked while driving or servicing a vehicle.

Let’s take a look at auxiliary brake basics.

Separate System

The standard brakes on your car make use of a hydraulic system that exerts pressure on either discs or drums to slow you down when you push the brake pedal. What is an auxiliary brake, then? It’s actually an additional system that operates entirely independently, which is why it’s also called the “emergency” brake — it will function even in the event that the regular brakes have failed.

How Is It Activated?

Most auxiliary brakes are mechanically activated by a cable, which is usually connected to a foot pedal on the far left of the driver’s side footwell, or a handle on the center console. On modern vehicles, the brake may be activated electronically by a button, or sometimes automatically when the vehicle is put into park.

How Does It Work?

Parking brake handleOnce activated, the auxiliary brake can work in one of a few different ways. If your vehicle has drum brakes at the rear, then the shoes inside of it are compressed mechanically so that they stop the motion of the back wheels. If you have disc brakes, there may be a separate, small drum brake assembly that is used exclusively by the parking brake, or you may have a small mechanical screw that moves the piston without the need for the hydraulic action of the brake fluid so that the disc is locked.

When Should You Use It?

With a manual transmission, you won’t likely wonder what is an auxiliary brake because you’ll use it all of the time when you park to ensure that your car or truck doesn’t roll away. With an automatic transmission, it’s rarer to apply it when the gearbox is set to “park,” but it’s still good practice — especially on steep hills. An auxiliary brake can also be used in the event that your regular brakes have failed, as it can serve as a last-ditch method of stopping the vehicle using just the rear wheels.

If you’ve ever wondered what an auxiliary brake is, it’s essentially the exact same thing as an emergency brake or a parking brake with a different name. It works in a similar fashion and should be used in a similar manner, too.

Check out all the brake system parts available on NAPA Online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on what an auxiliary brake is, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Creative Commons.

about author

Benjamin Hunting

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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