CDL Combination Vehicles TestDriving Combination Vehicles SafelyHard
A commercial driver is operating a combination vehicle and notices that the trailer is swaying excessively from side to side. The road is dry, and there's no strong crosswind. What is the most probable cause of this trailer sway?
- AThe trailer tires are overinflated, reducing traction.
- BImproper weight distribution within the trailer, with too much weight toward the rear.
- CThe fifth wheel coupling is not properly lubricated.
- DThe tractor's suspension system is worn out.
Show answer & explanationAnswer & explanation
Correct answer: B. Improper weight distribution within the trailer, with too much weight toward the rear.
Improper weight distribution, particularly with too much weight concentrated at the rear of the trailer, is a primary cause of excessive trailer sway. This shifts the center of gravity rearward, making the trailer unstable and prone to oscillation, even in ideal conditions.
Why the other options are wrong
- A. Overinflated tires would reduce the tire's contact patch and potentially reduce traction, but the primary effect related to sway is usually due to load distribution rather than tire pressure alone, especially if the sway is 'excessive'.
- C. Improper fifth wheel lubrication can cause steering difficulty, noise, or damage to components, but it's not a direct cause of trailer sway.
- D. Worn tractor suspension would primarily affect the tractor's ride and handling, not typically cause excessive trailer sway independently.
Trailer Sway Causes
Excessive trailer sway is most often caused by improper weight distribution, especially with too much weight loaded toward the rear of the trailer.
- Rear-heavy loads create a pendulum effect.
- Sway leads to instability and loss of control.
- Proper loading is crucial for stability.
Memory trick: Rear Weight Renders Rattle.