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Air Brakes Free CDL Practice Tests
Page 7

Prepare For The Air Brakes Portion Of Your CDL Written Exams

Air Brakes Questions

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Normally during anti-lock braking, the driver:
  • Will keep his foot on the pedal and keep applying pressure
  • Will swerve side-to-side
  • Will quickly press and release the brake pedal
  • Should stand on the brake pedal with both feet
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From The CDL Manual

For normal or emergency stopping using anti-lock brakes, the driver’s foot remains on the brake pedal in which the anti-lock module then acts as a foot pumping the air brake system. On the air-brake system the driver must pump or use stab braking in an emergency.

Next
In case of emergency stops, drivers should:
  • Find an incline to help stop the vehicle
  • Press the brake pedal as hard as they can
  • Try to run into something soft
  • Use stab or controlled braking methods
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From The CDL Manual

5.4.3 – Emergency Stops

If somebody suddenly pulls out in front of you, your natural response is to hit the brakes. This is a good response if there is enough distance to stop and you use the brakes correctly.

You should brake in a way that will keep your vehicle in a straight line and allow you to turn if it becomes necessary. You can use the "controlled braking" method or the "stab braking" method.

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Next
All of the following are factors in total stopping distance except:
  • Horizon distance
  • Brake lag distance
  • Perception distance
  • Reaction distance
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From The CDL Manual

Perception Distance + Reaction Distance + Brake Lag Distance + Effective Braking Distance = Total Stopping Distance

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Next
Average stopping distance under normal conditions at 55 mph is:
  • 450 feet
  • 100 feet
  • 32 feet
  • 450 yards
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From The CDL Manual

The air brake lag distance at 55 mph on dry pavement adds about 32 feet. Therefore, for an average driver traveling 55 mph under good traction and brake conditions, the total stopping distance is more than 300 feet. This is longer than a football field.

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Next
Compared to hydraulic brakes, air brakes add how much distance to an average 55 mph stop?
  • 300 feet
  • 55 feet
  • 100 feet
  • 32 feet
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From The CDL Manual

The air brake lag distance at 55 mph on dry pavement adds about 32 feet. Therefore, for an average driver traveling 55 mph under good traction and brake conditions, the total stopping distance is more than 300 feet. This is longer than a football field.

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Next
Total stopping distance with air brakes is Perception distance + Braking Distance + Brake Lag Distance +:
  • Air temperature
  • Reaction distance
  • Slope distance
  • Sight distance
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From The CDL Manual

Perception Distance + Reaction Distance + Brake Lag Distance + Effective Braking Distance = Total Stopping Distance

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Next
Brake fade is caused by:
  • Manufacturer's defect
  • Excessive heat due to excessive use of the brakes
  • Air temperature
  • Faulty emergency brake
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From The CDL Manual

However, brakes can fade or fail from excessive heat caused by using them too much and not relying on the engine braking effect.

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Next
The main factor in causing brake fade is:
  • Heat
  • Cold
  • Speed
  • Moisture
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From The CDL Manual

Braking creates heat, but brakes are designed to take a lot of heat. However, brakes can fade or fail from excessive heat caused by using them too much and not relying on the engine braking effect.

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Next
Besides heat, another cause of brake fade is:
  • Incompetent mechanics
  • Excessive cold
  • Steep uphill inclines
  • Out-of-adjustment brakes
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From The CDL Manual

Brake fade also is affected by adjustment. To safely control a vehicle, every brake must do its share of the work. Brakes out of adjustment will stop doing their share before those that are in adjustment.

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Next
The reduced stopping power caused by overuse of the service brakes and excessive heat is called:
  • Brake fade
  • Braking distance
  • Heat fade
  • Cut-out
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From The CDL Manual

Brake Fading or Failure —

Brakes are designed so brake shoes or pads rub against the brake drum or discs to slow the vehicle. Braking creates heat, but brakes are designed to take a lot of heat. However, brakes can fade or fail from excessive heat caused by using them too much and not relying on the engine braking effect.

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