During normal driving conditions, how are parking brakes held away from the drum?

Study for the South Carolina School Bus Driver Test. Use flashcards and multiple choice questions, each question offers hints and explanations. Prepare effectively for your exam!

The parking brakes are held away from the drum by air pressure in air brake systems, which is common in many school buses and larger vehicles. In a typical air brake system, when you engage the parking brake, air pressure is released from the brake chambers that normally press the brake shoes against the drums. This allows the brake shoes to retract and not come into contact with the drum, preventing friction and wear when the parking brake is not engaged.

When the parking brake is disengaged, air pressure in the system pushes the brake chamber diaphragm, causing the brake shoes to be pressed against the drum, thus applying the brakes. Therefore, the correct functioning of air pressure is crucial for the efficient operation of the parking brakes, ensuring safety and preventing unintended movement of the bus.

In contrast, other options pertain to different mechanisms or functions within the braking system, but they do not specifically refer to how the parking brakes are held away from the drum during normal driving conditions. The S-cam is a component used in the brake application but does not serve this purpose in parking brake operation. Hydraulic pressure and the brake pedal are also related to different types of braking systems and their functionality.

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