Tech Geek Featurette: Parking Brakes

Parking Brake Warning Light

Whoa, Nelly! When to use it, why it's there, and what to expect.

I was asked recently about parking brakes, something we often take for granted and many drivers never use at all.; So here's a quick primer.

Whether you call it a "parking brake", "emergency brake," or just "e-brake," it provides two distinct functions: * An "emergency brake" function, which can be used to slow or stop the vehicle in the event of a hydraulic brake system failure; or * A "parking brake" function, used to prevent the car from rolling when parked.

Emergency Brake Function: Because your parking brake doesn't use the same hydraulic system that your regular foot brake does, it can be used to slow or stop the car in the very unlikely event that the hydraulic system fails. Parking brakes located on the center console can also be used by a passenger in the event that the driver loses consciousness.; Gee, what a pleasant thought!

Parking Brake Function: Luckily, this is the more common use for your parking brake. It makes sure your car stays in the same place you left it. Safety experts recommend always setting the parking brake, and we tend to agree, especially on vehicles with manual transmissions.;

Parking on a hill with your transmission in gear can put a significant load on your transmission and engine mounts, so we recommend always setting your emergency brake with the car in neutral, and then selecting park or putting your car in gear and switching it off.; This puts the load instead;on your e-brake, which is designed to take it.; It also eliminates the nasty "clunk" coming from your automatic transmission car when you suddenly relieve all that tension by pulling the shift lever out of park.

If you have a front-wheel drive car, your e-brake can be especially useful in making sure your car doesn't go anywhere - especially in very slippery conditions. Putting your car in gear or "Park" helps prevent the front wheels from turning; setting the e-brake does the same to the rear.; When parking in the snow, there is twice the resistance to sliding away.

Certain failures of the engine, clutch, transmission, axles, or other driveline parts will allow the car to roll away even with the transmission in "Park" or in gear. The e-brake would, of course, still work, and may be the only way to keep the car from rolling.

There are a few situations when we recommend not using your e-brake:; Parking brakes are prone to seizing when it's very cold out due to ice forming inside the cables that lead from the lever to the rear brakes. This is even more likely to happen when the vehicle is parked for an extended period of time, so think twice about using your e-brake in those conditions.

Manufacturers are starting to roll out electronically-controlled e-brakes.; These are convenient because they free up interior space on the center console or in the driver's footwell. They also allow the computer to control a variety of convenience functions:

* Automatic Hill-Hold, which uses the e-brake to prevent the car from rolling back when starting out on a hill. * Stop and Go Traffic aids, that automatically apply the parking brake when you come to a stop.; This eliminates the need to keep your foot on the brake to prevent your car from creeping forward - and releases automatically when you hit the gas. * Automatic engagement, which automatically sets the brake any time the car is switched off or put in "Park."

It's important to remember that the e-brake won't necessarily;prevent your car from rolling away - it simply adds more resistance. It's not a substitute for leaving your car in gear or "Park", it's a supplemental safety feature.

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