Oklahoma CDL Permit Test - Air Brakes

Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.

On long and/or steep downgrades, you should primarily use engine braking to control the speed of your vehicle. Use your brakes only as a supplement to this effect.

When performing a static leakage test on a triple combination vehicle with air brakes, the leakage rate should be no more than 5 psi in one minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

If equipped, ABS is in addition to a vehicle's normal braking system and does not increase or decrease the braking power of any other system. ABS only activates when a vehicle's wheels are about to lock.

Spring brakes do not work on all axles. If your vehicle's spring brakes activate due to low pressure in an air brake system, your vehicle will need a longer distance to stop than usual, especially if you are carrying a heavy load.

An Anti-Lock Braking System (ABS) helps to provide additional control during hard braking, but does not necessarily shorten a vehicle's stopping distance.