Correct: When holding firm pressure on the service brake for one minute, a drop of no more than 3 psi is acceptable. This test helps confirm that the service brake circuit is airtight and functioning within safe limits.

Correct: The service brake engages and releases each time you press and release the brake pedal during normal driving. It is the primary braking system used for all routine speed reduction and stopping.

Correct: The air compressor is driven by the engine through gears or a v-belt, which means it builds air pressure whenever the engine is running. This is why air pressure rises during normal engine operation.

Correct: Some automatic drain valves include an electric heater to prevent the valve from freezing in cold temperatures. This helps ensure the drain function works reliably year-round, especially in winter conditions.

Correct: Air pressure should reach 85 to 100 psi within 45 seconds at operating engine speed, indicating a healthy compressor and properly functioning system. This timed check is a standard part of the pre-trip air brake test.

Correct: If a large steering correction is needed during controlled braking, you should release the brakes first to allow the wheels to grip for steering. Once the adjustment is made, braking can be reapplied as conditions allow.

Correct: Each brake application on a downgrade should last approximately 3 seconds, which is enough time to reduce speed by about 5 mph below your target safe speed. Releasing the brakes between applications allows them to cool before the next use.

Correct: Because spring brakes work in combination with the service brakes, their holding power is directly affected by the adjustment of the service brakes. Keeping service brakes properly adjusted ensures reliable parking brake performance.

Correct: The compressor cuts in at approximately 100 psi and cuts out at approximately 125 psi, maintaining pressure within a safe operating range. If the governor is not activating within these ranges, the system should be inspected.

Correct: On slippery roads, the sudden engagement of spring brakes can cause the vehicle to skid out of control due to the abrupt locking of wheels. This is an important safety consideration when parking or when air pressure drops unexpectedly in poor conditions.

Correct: Front wheel brakes are effective and safe under all driving conditions, including wet and icy roads. Avoiding their use based on conditions is unnecessary and can actually reduce overall stopping effectiveness.

Correct: The S-cam rotates when the brakes are applied, pushing the brake shoes outward against the drum to create stopping friction. It is a key mechanical component in the foundation brake assembly.

Correct: While a safety relief valve opening is a sign of a malfunction that should be addressed, it does not require an immediate stop. The driver should remain calm, monitor the system, and arrange for inspection at the next appropriate opportunity.

Correct: The engine should provide the primary braking effect on long or steep downgrades, using compression and drivetrain resistance to control speed. This preserves the service brakes for use when needed and prevents dangerous heat accumulation.

Correct: Effective stab braking combines applying maximum brake force, releasing when the wheels lock, and reapplying as soon as the wheels begin rolling again. This full sequence helps maintain steering control while achieving the shortest possible stop.

Correct: Each air tank has a drain valve at the bottom that allows accumulated moisture and oil to be removed. Regular draining through this valve is an important part of the pre-trip inspection and ongoing maintenance.

Correct: If the governor fails, the compressor may not maintain pressure within the proper range, creating unsafe braking conditions. A bus with a malfunctioning governor should not be operated until the issue is resolved.

Correct: The supply pressure gauge shows how much compressed air is currently stored in the air tank, giving the driver a real-time view of available braking power. Monitoring it regularly is an important part of safe operation.

Correct: Brake fade occurs when excessive heat causes chemical changes in the brake lining, reducing its ability to create friction and stopping power. This is why engine braking is recommended on long downgrades to prevent heat build-up.

Correct: Friction between brake shoes and drums generates significant heat, which brakes are designed to absorb and dissipate. Understanding this helps explain why overheating is a real risk during extended or repeated hard braking.