When do spring brakes fully engage?

The correct answer indicates that spring brakes fully engage when air pressure drops to between 20 and 45 PSI. This is a crucial safety feature in air brake systems found in larger vehicles such as trucks and buses.

When the air pressure in the brake system falls to this range, it signals a potential failure in the system. The spring brakes are designed to engage automatically as a fail-safe measure to prevent the vehicle from rolling. This mechanism ensures that if the air pressure drops too low, the vehicle will come to a stop, thereby enhancing safety and preventing accidents caused by brake failure.

The engagement of spring brakes is an important consideration for drivers of vehicles equipped with air brakes because maintaining proper air pressure is essential for safe vehicle operation. Understanding when and why spring brakes deploy can help drivers respond effectively to any issues with their braking system.