Parking brakes are necessities on some vehicles as is their service - While many drivers overlook these instruments, some vehicles make it impossible to do so. - Motor Age - Automotive training, certi
Parking brakes are necessities on some vehicles as is their serviceWhile many drivers overlook these instruments, some vehicles make it impossible to do so.
Publish date: Oct 1, 2009 By:Paul Zangari Source: Motor Age
Most calipers with integrated parking brakes use cable control, as on this 2008 Chevy Malibu. (PHOTO: PAUL ZANGARI)
For many drivers, parking brakes are an afterthought — if they're thought of — and that's not good. This too-often overlooked
system serves an important purpose. That purpose has nothing to do with emergencies; banish the term "emergency brake" from
your vocabulary! The parking brake is there to keep a stopped car where the driver put it, either by itself or backing up
the transmission.
Preventing Wear and Other Problems
Quick Fixes
Want proof too many drivers don't appreciate the importance of parking brakes? Just watch a busy, sloping parking area sometime.
How many arriving drivers hop out of vehicles that are still rocking back-and-forth? Too many just select Park and release
the footbrake. On an incline this lets the vehicle roll until something stops it. So the parking pawl (with an automatic)
catches or meshed gears meet (with an engaged stick) to arrest the motion — but not in one, smooth move. By the time the transmission
catches, momentum causes an opposite reaction, rocking the vehicle — sometimes several times. As a car or truck treated this
way ages, wear increases the distance and severity of the rocking motion, worsening wear on all parts concerned every time
the car rolls when the driver skips using the parking brake.
If anyone you observe letting a car rock and roll because they failed to apply the parking brake happen to be your own customers,
be sure to clue them in: Applying the brake costs nothing and can prevent costly driveline problems as well as (ironically)
parking brake failure. This can happen when disuse allows cables to corrode and seize — often grounds for a flunked safety
inspection.
Chrysler says that if there's contact between this pinchweld flange and the parking brake cable, the flange has got to go.
Not only does parking brake use help preserve harder-to-maintain drivetrain components (as well as the parking brake system
itself), on several models the rear brakes won't self-adjust unless the parking brake is used. Besides, parking brakes also
mean enough to safety officials that manufacturer-identified parking brake problems often lead to recalls. They shouldn't
be ignored.
Variations, Complications
1 Bolting an electric motor to the outside back of the bore chamber makes for a neat integration of the parking brake and
caliper.
For decades, parking brakes were pretty standard: a strut inside each rear drum brake engaged one shoe web, and in combination
with a lever engaging the other web, spread the shoes into contact with the drum when tugged by a cable. Pull for the cable
came either from a lever or pedal operated by the driver. Thanks to the simplicity and dependability of the system just described,
drum brakes will remain in use for some time. But more modern systems are providing plenty of company.
Adding the parking function to a disc brake has proven both a challenge and opportunity to engineers. Often, carmakers opt
for specialization — letting calipers grip rotors only to stop a car that's moving and adding a drum brake dedicated to parking
inside the hat section of the rotor. These drum-in-hat systems have been around at least since the four-disc 1966 Corvette.
Mechanically applying a caliper can be tricky, requiring a hole in the blind end of the bore for a moving shaft that then
needs to be sealed. Leaks here are possible. In older models we've also seen complications with internal moving parts when
brake fluid gets stale and corrosion intrudes.
Paul Zangari is a freelance writer specializing in technical autmotive subjects. He also is the host of a weekly radio show airing in Providence, R.I., called "Drive-Thru Radio" on station WPRO-AM.
Articles by Paul Zangari
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