When commercial vehicles negotiate tight turns, rear wheels follow a shorter path than the front wheels, creating an inward sweep known as off-tracking. Rank the following vehicle setups according to the extent of off-tracking produced, ordering them from the GREATEST swept path required to the LEAST swept path required when executing the same cornering maneuver.
- 1A combination tractor-semitrailer with a 41-foot distance from the kingpin to the center of the trailer rear tandem axles
- 2A single-unit commercial straight vehicle with a 26-foot wheelbase between the front and rear axles
- 3A two-axle medium-duty box truck with a 16-foot wheelbase between the front and rear axles
- 4A two-axle bobtail tractor with a 10-foot wheelbase operating without an attached trailer
Answer
From greatest to least off-tracking: tractor-semitrailer with 41-foot kingpin-to-tandem spacing, followed by the single-unit vehicle with a 26-foot wheelbase, then the medium-duty box truck with a 16-foot wheelbase, and finally the two-axle bobtail tractor with a 10-foot wheelbase.
Off-tracking occurs because rear wheels track inward toward the center of a turn relative to the steer tires. The magnitude of this cheat is governed directly by the effective wheelbase length (the distance from the steering axle or trailer kingpin to the rear axles). Therefore, the configuration with a 41-foot kingpin-to-tandem spacing produces the greatest off-tracking, followed sequentially by the 26-foot single-unit vehicle, the 16-foot box truck, and the 10-foot bobtail tractor.
Step-by-Step Solution
Key Concept
Off-tracking increases in direct proportion to the distance between the steering/pivot point and the rear axles of a vehicle.
Estimated Time:1m 0s