Examkin

Question

Difficulty: HardBalance and Center of Gravity

Determine whether the following statement regarding commercial vehicle balance and weight distribution is true or false: Concentrating dense freight behind the rear trailer tandem axles shifts the center of gravity rearward, which increases drive axle traction while reducing front steering axle weight and inducing trailer sway.

Answer: Answer

Answer

False
The statement is false because loading dense cargo behind the rear trailer axle group causes the suspension to act as a fulcrum. This levers weight upward off the fifth wheel, simultaneously reducing normal force and traction on the drive axles and steering axle while dramatically increasing the risk of trailer sway (fishtailing).

Step-by-Step Solution

1
Analyze the mechanical lever and fulcrum dynamics created by the trailer suspension.
The rear trailer tandem axles act as a pivot point (fulcrum). Weight placed behind this pivot exerts downward torque on the trailer overhang and an upward vertical force at the kingpin.
Cargo placed aft of the suspension pivot creates a counterbalancing teeter-totter effect relative to the front of the trailer.
2
Evaluate the effect of upward kingpin force on tractor axle loading and traction.
The upward force at the fifth wheel unloads the tractor chassis, reducing the normal force on both the drive axles and the front steering axle.
Reduced vertical load on the drive tires diminishes drive traction, while decreased steer axle weight causes light, unresponsive steering.
3
Assess vehicle dynamic stability resulting from a rearward-shifted center of gravity.
Concentrating weight at the extreme rear increases the trailer's polar moment of inertia, leading to hazardous lateral instability and trailer whip (fishtailing).
Mass distributed far behind the suspension pivot amplifies side-to-side oscillations during steering inputs or crosswinds.
4
Determine the truth value of the overall statement.
Because rear-overhang loading decreases drive axle traction rather than increasing it, the statement is completely false.
A statement containing a false premise regarding axle traction mechanics is factually incorrect.

Key Concept

Trailer fulcrum effect, axle weight transfer, and center of gravity balance
Estimated Time:1m 30s
Rate this question

Topics

Balance and Center of Gravity

More questions from this topic