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5.4.5 – Brake Fading or Failure

Brakes are designed so brake shoes or pads rub against the brake drum or disks 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.

Excessive use of the service brakes results in overheating and leads to brake fade. Brake fade results from excessive heat causing chemical changes in the brake lining, which reduce friction and also causing expansion of the brake drums. As the overheated drums expand, the brake shoes and linings have to move farther to contact the drums, and the force of this contact is reduced. Continued overuse may increase brake fade until the vehicle cannot be slowed down or stopped.

The brake adjustment will also affect brake fade. 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. The other brakes can then overheat and fade, and there will not be enough braking available to control the vehicle(s). Brakes can get out of adjustment quickly, especially when they are hot. Therefore, check brake adjustment often.

5.4.6 – Proper Braking Technique

Remember: The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear, the following is the proper braking technique:

  • 1. Apply the brakes just hard enough to feel a definite slowdown.
  • 2. When your speed has been reduced to approximately 5 mph below your “safe” speed, release the brakes. (This application should last for about three seconds.)
  • 3. When your speed has increased to your “safe” speed, repeat Steps 1 and 2.

For example, if your “safe” speed is 40 mph, you would not apply the brakes until your speed reaches 40 mph. You now apply the brakes hard enough to gradually reduce your speed to 35 mph and then release the brakes. Repeat this as often as necessary until you have reached the end of the downgrade.

Multiple-Choice Questions:

Question #295 (1 of 6)

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Brake adjustment can affect brake fade. Describe how:

  • Brakes out of adjustment will stop doing their share before those that are in adjustment. The air pressure can build up from the heat, and there will not be enough braking available to control the vehicle(s). Air pressure must be reduced to resume proper braking.
  • Brakes that are in adjustment will stop doing their share before those that are out of adjustment. The other brakes can then overheat and fade, and there will not be enough braking available to control the vehicle(s).
  • All of these are correct
  • Brakes out of adjustment will stop doing their share before those that are in adjustment. The other brakes can then overheat and fade, and there will not be enough braking available to control the vehicle(s).
Brakes out of adjustment will stop doing their share before those that are in adjustment. The other brakes can then overheat and fade, and there will not be enough braking available to control the vehicle(s).
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Question #296 (2 of 6)

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Which of the following statements is true?

  • The use of engine brakes on a long and/or steep downgrade is only recommended in the rain or on slick roads. On dry roads, do not use the foot brake.
  • The use of brakes on a long and/or steep downgrade is only useful in an emergency when you have lost the braking effect of the engine
  • The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine
  • The braking effect of the engine is only helpful on grades steeper than 5%
The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine
If you have the engine in the proper gear, the engine brake will do most of the work. You will only use the foot brake occasionally to keep the truck in the proper speed range.
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Question #294 (3 of 6)

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Describe what happens during brake fade:

  • None of these are correct
  • As the overheated drums expand, the S-cam has to move farther to contact the drums, and the force of this contact is increased. Continued overuse may increase brake fade until the vehicle cannot be slowed down or stopped.
  • As the overheated brake chambers expand, the air pressure drops and the brake shoes and linings have to move farther to contact the drums. Decreased air pressure won't allow proper braking pressure. Continued overuse may increase brake fade until the vehicle cannot be slowed down or stopped.
  • As the overheated drums expand, the brake shoes and linings have to move farther to contact the drums, and the force of this contact is reduced. Continued overuse may increase brake fade until the vehicle cannot be slowed down or stopped.
Excessive use of the service brakes results in overheating and leads to brake fade. Brake fade results from excessive heat causing chemical changes in the brake lining, which reduce friction and also causing expansion of the brake drums. As the overheated drums expand, the brake shoes and linings have to move farther to contact the drums, and the force of this contact is reduced. Continued overuse may increase brake fade until the vehicle cannot be slowed down or stopped.
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Question #297 (4 of 6)

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Once the vehicle is in the proper low gear, the following is the proper braking technique:

  • 1. Apply the brakes just hard enough to feel a definite slowdown.
    2. When your speed has been reduced to approximately 5 mph below your “safe” speed, release the brakes. (This application should last for about three seconds.)
    3. When your speed has increased to your “safe” speed, repeat Steps 1 and 2.

  • 1. Apply the brakes just hard enough to feel a definite slowdown.
    2. When your speed has been reduced to approximately 10 mph above your “safe” speed, release the brakes. (This release should last for about three seconds.)
    3. When your speed has increased to 10 mph above your “safe” speed, repeat Steps 1 and 2.

  • 1. Apply the brakes just hard enough to feel a definite slowdown.
    2. When your speed has been reduced to approximately 15 mph below your “safe” speed, release the brakes. (This application should last for about three seconds.)
    3. When your speed has increased to your “safe” speed, repeat Steps 1 and 2.

  • 1. Apply the brakes just hard enough to feel a definite slowdown.
    2. When your speed has increased to approximately 5 mph above your “safe” speed, release the brakes.
    3. When your speed has increased to 10 mph above your “safe” speed, repeat Steps 1 and 2.

Remember: The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear, the following is the proper braking technique:

  • 1. Apply the brakes just hard enough to feel a definite slowdown.
  • 2. When your speed has been reduced to approximately 5 mph below your “safe” speed, release the brakes. (This application should last for about three seconds.)
  • 3. When your speed has increased to your “safe” speed, repeat Steps 1 and 2.
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Question #298 (5 of 6)

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Let's say you're braking down a long, steep grade and your "safe" speed is 40 mph. When your speed reaches 40 mph, what do you do?

  • Allow the vehicle to increase its speed to 45 mph, then apply the brakes hard enough to gradually reduce your speed to 25 mph and then release the brakes
  • Allow the vehicle to increase its speed to 50 mph, then apply the brakes hard enough to gradually reduce your speed to 40 mph and then release the brakes
  • Apply the brakes hard enough to gradually reduce your speed to 35 mph and then release the brakes
  • Apply the brakes hard enough to gradually reduce your speed to 30 mph and then release the brakes
For example, if your “safe” speed is 40 mph, you would not apply the brakes until your speed reaches 40 mph. You now apply the brakes hard enough to gradually reduce your speed to 35 mph and then release the brakes. Repeat this as often as necessary until you have reached the end of the downgrade.
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Question #293 (6 of 6)

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Excessive use of the service brakes results in:

  • Too much air pressure and leads to brake binding
  • Overheating and leads to brake fade
  • Too little air pressure and leads to brake fade
  • None of these are correct
Excessive use of the service brakes results in overheating and leads to brake fade.
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