36. Pre-trip - Undertanding the Air Pressure Gauges - Class B CDL School Bus

In this segment, I explain the connection between the air-brake test script and the air pressure gauges.
The numbers you must memorize (if you test in the state of Georgia) are:
Air pressure must reach approx. 120 psi (burst of air)
Initial drop: no more than 15 psi
Additional drop: no more than 3 psi / min.
Low air pressure warning signal: occurs before air pressure reaches 55 psi
Spring brake / parking brake engage: occurs at approx. 40 psi
For more details, refer to your state's Department of Motor Vehicles-issued Commercial Driver's License Manual.