Instead of a standard passenger vehicle hydraulic braking system, heavy vehicles rely on compressed air within their braking systems to effectively stop. Utilizing air tanks and an air compressor, the air is kept pressurized in anticipation of the brake pedal being depressed for immediate response.
An air brake test verifies the functioning of the brakes. Check the air leakage rate to determine if any loss of air is within specification, normally 2 psi or less for one vehicle, and 3 psi for multiple attached vehicles, like trailers. Additionally, make sure that the pressure build up functions, as well as the low pressure warning signal.
You should verify the functionality of the parking, spring and service brakes as well. All the brakes combined, create a safe braking system for the open road.
