Cargo, Weight Distribution, and Rollover Prevention
Cargo, Weight Distribution, and Rollover Prevention
This domain tests load securement, axle and gross weight limits, and the stability choices that keep a combination upright. The exam expects you to think in terms of axle loads and center of gravity, not just total weight.
Weight distribution
Check gross vehicle weight, gross combination weight, axle ratings, tire ratings, and bridge-formula limits. Place heavy freight low and centered over the axles. Too much weight behind the trailer axles can lift the tractor’s steer axle and reduce steering control; too much on the steer axle can overload it. Slide the trailer axles or reposition the load to bring each axle within rating.
Securement
Use tiedowns with adequate working load limits in good condition. The securement system must resist forward, rearward, and sideways forces; aggregate tiedown strength must be sufficient for the load. Recheck straps and chains after the first few miles and after any load shift.
Rollover prevention
A high center of gravity, a loose load, excessive speed in a curve, and sudden steering all raise rollover risk. Slow down before the curve, keep the load low, and avoid sharp corrections. A combination does not “grip” like a car; the trailer can push the tractor sideways.
Worked example
A load leaves the steer axle at 10,500 lb, the drive axles at 19,000 lb, and the trailer axles at 17,000 lb. Ratings are 12,000, 20,000, and 20,000 lb. The axles are legal, but the load is far back and steering feels light. Moving the load forward or sliding the trailer axles restores steer-axle weight without overloading the drives.
Traps
Checking only gross weight, ignoring tire and axle ratings, failing to recheck securement, and carrying a high center of gravity too fast into a ramp or curve.