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CDL Air Brakes Cheat Sheet

The 56 highest-yield CDL Air Brakes questions with the correct answer and one line of logic each - plus the walk-in document checklist and the signs you must know on sight. Print it, mark it up, walk in calm.

  • 56 exam-style questions with answers and explanations
  • Walk-in checklist: documents, fees, vision test - printable with checkboxes
  • 12 must-know road signs with plain-English meanings
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CDL Air Brakes
56 questions inside

Free preview - 5 of the questions inside

1. A dual air brake system has:
✓ Two separate air brake systems using one set of controls
A dual air brake system uses two separate air systems - a primary and a secondary - that share one set of brake controls. If one system fails, the other can still brake the vehicle, though with reduced power. Most newer heavy vehicles have dual air brakes for this added safety.
2. Controlled braking means:
✓ Applying the brakes as hard as you can without locking the wheels
Controlled braking is applying the brakes firmly, as hard as possible without locking the wheels, so you can keep steering. If a wheel locks, ease off just enough to let it roll. It's a key emergency technique on vehicles without ABS.
3. The most common type of foundation brake found on heavy vehicles is the:
✓ S-cam drum brake
The S-cam drum brake is the most common foundation brake on heavy vehicles. Air pressure moves a pushrod and slack adjuster that turns an S-shaped cam, forcing the brake shoes against the drum. Knowing how it works helps you inspect and understand braking.
4. The supply pressure gauge shows:
✓ How much air pressure is in the tanks
The supply pressure gauge (or gauges, on dual systems) shows how much air pressure is in the storage tanks. You watch it to make sure pressure stays in the normal range and builds up before driving. A drop in supply pressure warns of a leak or a compressor problem.
5. To test the low air pressure warning, you should:
✓ With the engine off and pressure charged, step on and off the brake to reduce pressure until the warning comes on
With the system charged and the engine off, rapidly apply and release the brake pedal to use up air; the low air warning should come on before pressure drops below 60 psi. This confirms the warning works before you rely on it. A warning that doesn't activate must be repaired.
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51 more questions in the PDF