CDL General Knowledge TestAir Brakes (if applicable)Easy
When inspecting the air brake system, a driver should check that the brake pedal has no more than approximately how much free play before the brakes begin to engage?
- A2 inches
- B1 inch
- C1/2 inch
- D3 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 1 inch
Proper brake pedal free play is crucial for effective air brake operation. Excessive free play can indicate maladjusted brakes or other issues, while too little can lead to dragging brakes. The standard maximum free play is approximately 1 inch.
Why the other options are wrong
- A. 2 inches is excessive free play, indicating potential issues like maladjusted brakes.
- C. 1/2 inch is generally too little free play, which could indicate a problem or lead to dragging brakes.
- D. 3 inches is far too much free play, suggesting a serious problem with the brake system.
Brake Pedal Free Play (Air Brakes)
Brake pedal free play refers to the distance the brake pedal can be depressed before the brakes begin to engage. Proper free play is essential for effective braking and prevents dragging.
- Maximum free play is about 1 inch.
- Excessive free play can indicate maladjustment.
- Too little free play can cause brakes to drag.
Memory trick: The brake pedal should have just enough 'wiggle room' – about one thumb's width – before it starts to work.