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Air Brake System Parts and How They Work
Air brakes use compressed air to make a heavy vehicle stop. They are a safe and effective way to stop large trucks and buses because air is always available and the system stores a reserve of pressure, so a small leak will not immediately stop the brakes from working. But an air brake system has many parts and takes more skill to inspect and use than a hydraulic system. This chapter explains the major components: how air is made and stored, how it is turned into braking force at the wheels, the spring brakes that stop you if air is lost, and the dual-system design that gives heavy vehicles a backup. Understanding each part helps you recognize problems during inspection and drive safely.
Inspecting Air Brakes
Air brakes have more parts than hydraulic brakes, so a thorough inspection is essential before every trip. A proper air brake inspection confirms that the compressor and governor build and control pressure correctly, that the low-pressure warning and spring brakes work, that the system does not leak too much, and that the mechanical parts at each wheel are in safe condition. The CDL air brake test includes a specific set of checks you must perform in order, ending with a test of the service and parking brakes as you begin to move. This chapter walks through those checks, the pressure numbers you must know, and the wheel-by-wheel items that keep your brakes reliable.
Using Air Brakes Safely
Driving with air brakes safely means understanding that heavy vehicles need much more room to stop than cars, that air brakes add a short lag before they take hold, and that heat is the enemy of braking on long downgrades. This chapter covers how to calculate total stopping distance, how to brake normally and in emergencies, how to keep brakes from fading on hills by choosing the right gear and using proper braking technique, and what to do when the low air pressure warning comes on. Mastering these skills protects you, your load, and everyone around you, because a heavy vehicle that cannot stop in time is extremely dangerous.
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