Mountain Driving: Grades, Brake Heat, and Escape Ramps
Mountain Driving tests descent strategy, because on a long grade brake heat, not horsepower, decides whether you arrive.
Before the descent
- Check the brakes and air pressure at the top and test the brakes at low speed.
- Select the gear you climbed in; if fourth was needed to climb, descend in fourth or lower.
- Never descend in neutral or with the clutch disengaged.
On the descent
- Snub braking: brake firmly to shed five to ten mph, release, and let the drums cool between applications. Continuous light pressure overheats drums and glazes linings.
- Watch the air gauge. Fanning the brakes consumes air that a long grade will not give back.
- If you smell smoke or the pedal fades, pull off and let the brakes cool before continuing.
- Escape ramps are gravel beds or arrestor beds: aim for the middle and do not try to steer out halfway.
Worked example
A loaded truck starts down a seven percent grade three miles long, at 35 mph in fifth. You shift to fourth at 30 mph before the grade steepens, then snub off five mph about every 30 seconds. Waiting to downshift until 50 mph is the mistake: by then the engine over-revs or you fry the brakes trying to slow down.
Traps that cost marks
- Riding the brakes lightly the whole way down.
- Downshifting after the brakes are already hot and fading.
- Ignoring the air gauge on a long descent.
- Using the parking brake on hot drums as a routine descent tool.