CDL Air Brake Brake Fade and Downgrade Driving 1 — Questions and Answers
Question 1: What is brake fade?
- A gradual increase in braking efficiency over time
- The loss of braking power caused by overheated brakes (Correct answer)
- The automatic adjustment of brake pressure on hills
- The reduction in stopping distance on wet roads
Correct answer: The loss of braking power caused by overheated brakes
Brake fade occurs when brakes overheat, causing a significant loss of braking effectiveness that can be extremely dangerous on long downgrades.
Question 2: What is the correct technique for driving down a long, steep grade with air brakes?
- Ride the brakes continuously while staying in a higher gear
- Select a low gear before starting down and use controlled, intermittent brake applications (Correct answer)
- Use only the engine brake and avoid the air brakes entirely
- Shift to neutral to save fuel and use brakes as needed
Correct answer: Select a low gear before starting down and use controlled, intermittent brake applications
Select a low gear before descending so engine braking helps control speed, and use controlled applications rather than continuous braking to prevent overheating.
Question 3: What is 'snub braking' when used on a downgrade?
- Pumping the brakes rapidly to build air pressure
- Applying brakes firmly to reduce speed by about 5 mph, then releasing until speed rises again (Correct answer)
- Using only trailer brakes on steep grades
- Applying maximum brake pressure continuously throughout the descent
Correct answer: Applying brakes firmly to reduce speed by about 5 mph, then releasing until speed rises again
Snub braking means applying brakes firmly to slow about 5 mph below your target speed, then releasing so brakes can cool before the next application.
Question 4: What is a safe speed limit when driving down a long, steep grade?
- The posted speed limit for the grade
- 5 mph above the speed you could manage without brakes
- 55 mph regardless of grade steepness
- A speed at which you could still control the vehicle if brakes failed completely (Correct answer)
Correct answer: A speed at which you could still control the vehicle if brakes failed completely
Your safe downgrade speed is one at which you could still safely control the vehicle even if your brakes completely failed.
Question 5: How does brake fade affect stopping distance?
- Stopping distance decreases as brakes get hotter
- Stopping distance remains the same regardless of temperature
- Stopping distance increases significantly as brakes overheat (Correct answer)
- Stopping distance only changes on wet roads
Correct answer: Stopping distance increases significantly as brakes overheat
As brakes overheat and fade, stopping distance can increase dramatically, making it impossible to stop within a safe distance.
Question 6: What is 'glazing' in the context of brake drums?
- Applying a protective coating to brake drums
- A smooth, hard surface that forms on overheated brake drums, reducing friction (Correct answer)
- Ice formation on brake drums in cold weather
- The normal wear pattern on new brake drums
Correct answer: A smooth, hard surface that forms on overheated brake drums, reducing friction
Glazing occurs when overheated brake drums develop a smooth, hard surface that significantly reduces friction and braking effectiveness.
CDL Air Brake Brake Fade and Downgrade Driving 1
What is brake fade?