Arizona Air Brakes CDL Practice Test

When should you avoid using the parking brake?

1. On steep hills

2. If the air pressure is low

3. When the brakes are hot

4. Any time you park

The correct answer is: When the brakes are hot

Using the parking brake is essential for securing a vehicle when parked, but certain conditions can make its use inadvisable. The correct answer highlights the importance of not using the parking brake when the brakes are hot. When brakes are hot, they have expanded due to heat generated from use. Applying the parking brake can cause the brake components to seize or stick together as they cool. This is particularly problematic with drum brakes, which can contract unevenly and lead to engagement issues. If the parking brake is used under these circumstances, it may not release properly when you need to drive again, potentially leading to safety hazards or damage to the braking system. In contrast, using the parking brake on steep hills is often encouraged to secure the vehicle. Avoiding it when air pressure is low may also be valid, but it's not as directly related to heat as in this case. Parking in any situation without considering brake conditions wouldn't focus on the specific dangers associated with hot brakes, thus further affirming why this specific response holds relevance in the context of proper brake usage.