Is it an emergency brake or a parking brake?

Why are cars still equipped with two braking systems? Because of safety, or is it redundancy?

On modern cars, well, not really. Cars manufactured in days long past had four-wheel drum brakes that worked sort of OK but not nearly as well as modern cars.

Those early cars did have hydraulic brake systems but they were activated by a single-piston master cylinder. On those cars and trucks, the parking brake actually was the emergency brake and often was used as such when the single-piston master cylinder failed.

Now on modern cars, we have dual-piston master cylinders with all sorts of computerized electric-over-hydraulic activation systems for the brakes including anti-lock (all cars of today are equipped with anti-lock brakes on at least one axle).

Total brake failure is virtually impossible. If the master cylinder begins to fail, there is the classic sinking brake pedal often accompanied by an amber or red "brake" light shining at you in the dash display. The car will still stop when this happens.

So why do we still have the emergency brake installed on cars? This is my theory: It's simply a parking brake.

I can count at least a thousand times where I have worked on cars where the parking brake would not activate. The parking brake typically is cable operated by a hand or foot lever with a ratcheting lock. Most parking brake problems are due to rusted activation cables. These cables get rusted and locked up mostly because of lack of use.

I hear comments like this from customers who insist on not using the parking brake: "I don't need to set the brake. The transmission is in park and the car won't move."

This statement is half true. In most cases, the car won't move when the automatic transmission is in "park" or the manual transmission is in gear.

However, I strongly urge all operators of motor vehicles to set the parking brake every time the vehicle is parked for three reasons. First, in the automatic transmission, the parking pawl (the part that locks the transmission not allowing the car to move) is a piece of stamped steel or aluminum resembling a bottletop opener but about a tenth the size of most bottletop openers. Are you going to trust the teeny piece of metal to hold back your 4,000-pound car?

Second, the parking brake is almost always connected to the self adjusters on the mechanical portion of the brakes at each wheel. When the parking brake is applied, the brakes will self adjust for the best performance. If you don't used the parking brake, your car's brakes may be out of adjustment.

Thirdly, a thief can circumvent the transmission linkage, move the selector to "neutral" and load your car onto a towing trailer or other tow vehicle without ever breaking into the passenger compartment. If you set the brake, the bad guy cannot move the car!

Another tip to avoid theft would be to turn the steering wheel about half a turn or more when you pull out the key, locking the steering wheels crooked. This makes moving the vehicle in a desired direction very difficult if the bad guy can't access the passenger compartment.

John Salem will answer online posts to this column at kdminer.com or write to him at gearbox@npgcable.com. This column is dedicated to help the motoring public solve their automotive problems. Salem is an L1-rated, ASE-certified master automobile technician and has owned and operated Salem & Sons Auto in Kingman for more than 17 years.