The air brake test is one of the few things on the pre-trip inspection that needs to be memorized. It is also the only automatic fail on the cdl test if not performed. There are basically 4 parts to remember.

 1. Check the truck parking brake. Leave the truck parking brake set (yellow nob out) and the trailer brake released (red nob in). Now put the truck in gear and gently pull against the parking brake.

 2. Check the service brake. Make sure the brakes are released (both nobs in), put in gear, and slowly pull forward to 5 mph. Now stop with the hands off the wheel and look for movement in the steering wheel. If it turns right or left the brakes are tighter on that side and need to be adjusted.

 3. Check for leaks. With the engine turned off, hold the brake pedal down for 1 minute and look for no more than 4psi of pressure loss on the primary air gauge.

4. Check the emergency systems in case of a leak. With the key on and the engine off, fan the brakes and lose the air pressure intentionally. The emergency light and buzzer should come on at 60psi, and the emergency spring brakes should come on (both nobs pop out) between 20 and 40 psi.

 In summary, there are 4 parts to the brake test, Two with the truck running and two with it off. This test is crucial for the cdl exam, and should be used on a regular basis in the work place as well.
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