At what PSI does the air brake system stop pumping air?

The air brake system is designed to stop pumping air at 120 psi to ensure optimal performance while maintaining safe operational parameters. This pressure threshold is significant because it is higher than the minimum required for proper brake function, allowing the system to effectively engage when needed. If the system continues to pump air beyond this point, it could lead to over-pressurization and potential system failure.

Understanding this pressure point is crucial for school bus drivers, as it helps them monitor the air brake system's health and determine when a maintenance check may be required. Maintaining the air pressure within the designated range ensures reliable braking performance, which is critical for the safety of both the driver and passengers.