Vehicle Systems, Inspection & Mountain Driving
14 free questions, part of the General Knowledge CDL practice test
This section covers pre-trip and en route inspection standards, like steering play, tire tread depth, and ABS systems, plus how to control a loaded rig on a mountain grade. Steering wheel play over 10 degrees, about 2 inches of movement at the rim, is a defect, and steering-axle tires need at least 4/32 inch of tread. For descents, the rule is to select the same low gear you'd need to climb the grade, then use snub braking to hold your speed.
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Start Class A CDL Theory ($15)Questions about Vehicle Systems, Inspection & Mountain Driving
How much steering wheel play is considered a defect?
More than 10 degrees of play, which is about 2 inches of movement at the rim of a 20-inch steering wheel.
What's the minimum tire tread depth on a steering axle?
4/32 of an inch. Other axle positions have a lower minimum, but steering axle tires are held to that stricter standard.
What is snub braking on a mountain descent?
Apply the brakes hard enough to get a definite slowdown, release once your speed drops about 5 mph below your safe speed, let it climb back up to that safe speed, then repeat the cycle down the grade.