Overweight Trailer Tandems and a Sliding Tandem Adjustment
You scale a five-axle combination at a roadside scale. The readings are: steer axle 11,400 lb; drive tandems 33,700 lb; trailer tandems 34,300 lb; gross 79,400 lb. The posted limits are 12,000 lb for the steer axle, 34,000 lb for each tandem group, and 80,000 lb gross. The scale has a 500-lb tolerance, but the state patrol is weighing nearby, and you are 300 lb over on the trailer tandems. Your trailer has a sliding tandem with holes every 6 inches. You do not know the exact weight-transfer rate per hole. The load is a secured 24,000-lb steel coil centered 36 inches ahead of the trailer midpoint. You have a wrench and can re-scale at the same facility. The fifth wheel is in the rear position. Your next appointment is in 40 minutes.
1. Which direction should you slide the trailer tandems, and why? What is the risk of sliding too far?
Read the worked answer
Initial capacity: steer has 600 lb left, drive has 300 lb left, trailer is 300 lb over, and gross is 600 lb under the 80,000-lb limit. Moving the trailer tandems rearward increases the load on the kingpin and reduces the load on the trailer tandems, so that is the correct direction to move weight off the trailer axle group. Do not guess the number of holes. Move one hole at a time and re-scale, because too much rearward movement can overload the drive or steer axles and change handling.
2. After moving one hole, the scale reads steer 11,500 lb, drive 33,900 lb, and trailer 34,000 lb. Is that legal, and what else should you check before accepting it?
Read the worked answer
The axle readings are within the posted limits and the gross remains 79,400 lb, so the axle weights themselves are legal. Do not stop at the scale ticket alone. Check tire ratings, registered weight, and any bridge-formula or local axle-spacing limit. Confirm the slider pins are fully engaged and the tandem is locked. If a local limit or the scale tolerance makes 34,000 lb too close, adjust the load or fifth wheel rather than sliding another hole blindly.
3. What should you verify after any tandem adjustment before entering traffic?
Read the worked answer
Re-scale after every adjustment. Check that the trailer tandems are locked, the air lines and electrical cord have enough slack, and the trailer tires clear the tractor frame and mud flaps through a turn. Sliding tandems changes off-tracking and turning clearance, so do a slow test turn before entering traffic. If the next hole would put drive or steer over a limit, stop and change the load position or fifth wheel setting instead of chasing the trailer axle number alone.