How much air pressure is acceptable to lose when applying the service brake for one minute?

When applying the service brake for one minute, losing no more than 4 psi is acceptable. This standard is set to ensure that the air braking system is functioning effectively and can maintain sufficient air pressure to operate safely. If the pressure drop exceeds this threshold, it may indicate potential leaks or issues within the braking system, which can compromise safety. Maintaining this limit is crucial for the reliable performance of the vehicle's braking system and is a key part of the pre-trip inspection process. Ensuring that the brake system holds pressure well is critical for the overall safety and functionality of the vehicle on the road.