Brake Fade and Downgrade Driving Flashcards

What is the purpose of a jake brake (engine compression brake)?

Answer: To use engine compression to slow the vehicle, reducing reliance on service brakes

An engine compression brake uses engine compression to retard vehicle speed, reducing heat buildup in service brakes on long downgrades.

When should a jake brake (engine compression brake) typically NOT be used?

Answer: On slippery or icy roads where it could cause drive wheels to skid

Engine compression brakes on slippery roads can cause drive wheels to lock up and skid, especially on lightly loaded or empty vehicles.

What does 'total stopping distance' include for a truck equipped with air brakes?

Answer: Perception distance + reaction distance + brake lag distance + effective braking distance

Total stopping distance includes perception distance, reaction distance, brake lag (air pressure build-up delay), and effective braking distance once brakes are applied.

What is brake lag distance in an air brake system?

Answer: The distance traveled while air pressure builds up to physically apply the brakes after the pedal is pressed

Brake lag is the distance the vehicle travels while air pressure builds to actually apply the brakes after the pedal is pressed, which can be up to 0.4 seconds.

At 55 mph, approximately how far does a fully loaded truck travel during the brake lag period before brakes engage?

Answer: About 32 feet

At 55 mph, a vehicle travels approximately 32 feet during the brake lag period before air pressure builds enough to engage the brakes.

Why does total stopping distance increase significantly on downgrades compared to level roads?

Answer: Gravity continuously accelerates the vehicle, adding to momentum and requiring more distance to stop

On downgrades, gravity continuously accelerates the vehicle, increasing its momentum and requiring a much greater stopping distance.