Georgia Commercial Driver License Practice Test

At what air pressure range will spring brakes generally bring a straight truck or tractor to a stop?

1. 0 to 20 psi

2. 20 to 45 psi

3. 45 to 60 psi

4. 60 to 80 psi

The correct answer is: 20 to 45 psi

Spring brakes are designed to engage automatically when air pressure in the braking system falls below a certain threshold. Typically, this threshold is within the range of 20 to 45 psi. When the air pressure drops to this level, the spring brakes activate to provide a fail-safe method of stopping the vehicle. This is crucial for maintaining safety in the event of a loss of air pressure, as it ensures that the vehicle can come to a stop even if the primary air system fails. Understanding the air pressure levels is important because it highlights the function of spring brakes as a secondary braking system. It also emphasizes the need for drivers to regularly monitor air pressure levels to prevent unintentional engagement of the spring brakes, which could lead to sudden stops or loss of control of the vehicle. Proper knowledge of these air pressure specifications is vital for safe operations in commercial driving.