Michigan CDL - Air Brakes Practice Exam

During a static leakage test, what is the maximum allowable rate for a double combination vehicle with air brakes?

1. 5 psi in one minute

2. 4 psi in one minute

3. 2 psi in one minute

4. 3 psi in one minute

The correct answer is: 3 psi in one minute

The maximum allowable rate for a static leakage test on a double combination vehicle with air brakes is 3 psi in one minute. This standard is established to ensure that the air brake system is functioning properly and can maintain adequate pressure for safe operation. Maintaining a low rate of air loss is crucial for ensuring the reliability and efficiency of the braking system. If a vehicle loses more than 3 psi in one minute during the static leakage test, it would indicate that there may be a leak in the air system, which could compromise the brakes' effectiveness. Therefore, the 3 psi threshold helps ensure that the air brake system is sealed and capable of maintaining the necessary air pressure for braking performance. In the context of the other choices, any higher psi loss (like 4 psi or 5 psi) would exceed acceptable limits, suggesting potential issues with the braking system that could endanger the vehicle's operation. Thus, the answer reflects a critical safety standard pertinent to commercial drivers operating vehicles with air brakes.