How much pressure drop is considered unacceptable in the pressure reserve test after applying the brakes?

In the context of the pressure reserve test, an unacceptable pressure drop is indicative of potential issues within the vehicle's braking system. When brakes are applied, the system should maintain a certain level of pressure to ensure functionality and safety. A drop of 20% of the first reading signifies a significant compromise in the system's ability to maintain pressure, which could lead to inadequate braking performance.

This value is determined based on standards for brake system integrity. If the pressure drop exceeds this threshold, it suggests that the system might have leaks or other defects that could be dangerous while operating the vehicle. Maintaining the pressure above this limit is crucial for ensuring that the brakes will function effectively in emergency situations or during regular driving.

Understanding the implications of a 20% drop in pressure helps technicians to assess the reliability of the brake system and take necessary corrective measures to ensure the safety of the vehicle and its occupants.