In the engine-off air brake test, the acceptable pressure drop after one minute on straight chassis is which value?

• A. Less than 2 psi
• B. Less than 3 psi
• C. Less than 4 psi
• D. Less than 5 psi

Answer: (B)

The test checks how much air pressure leaks from the system when the engine is off, by watching how much pressure drops in one minute with brakes released. For straight-chassis vehicles, the acceptable drop is less than 3 psi in one minute. This limit ensures the system can hold enough pressure without losing brakes too quickly due to leaks in hoses, fittings, valves, or other components. If the pressure falls more than 3 psi, it indicates leaks that need inspection and repair. The other options don’t match the defined threshold: 4 or 5 psi exceed the allowable leakage, while 2 psi is stricter than the standard but the official limit is 3 psi.