After reaching a mountain summit, a driver prepares to descend a prolonged 6% grade with several sharp switchbacks. To prevent thermal brake fade and maintain full steering control throughout the descent, which strategy should the driver implement?
- Shift into a lower gear prior to beginning the descent to utilize engine braking, and use brief, firm brake applications only when speed builds up.Answer
- BMaintain the posted speed limit by applying continuous light pressure on the brake pedal along the entire downgrade.
- CShift the vehicle into neutral to coast down the grade, applying the foot brake only when negotiating sharp switchbacks.
- DRemain in high gear and pump the brake pedal rapidly continuously to hold a uniform speed down the mountain slope.
Answer
Shift into a lower gear prior to beginning the descent to utilize engine braking, and use brief, firm brake applications only when speed builds up.
The primary cause of runaway vehicles on steep downgrades is thermal brake fade caused by overheating friction components. Downshifting into a lower gear before starting downhill allows engine compression to assist in speed control. Combining engine braking with brief, firm brake applications allows the brake system time to cool down between uses.
Step-by-Step Solution
Key Concept
Engine braking and brake heat management on steep downhill grades
Estimated Time:1m 15s