Most of the time, drivers have problems moving their tandems backwards, to take weight off of their trailer tandems. But there are a couple of situations where drivers need to be careful of how far forward they move their tandems.

Issue number 1

The first issue is bridge laws, at a certain distance you will not be able to load as much weight onto your vehicle. When the distance between the first axle of your tandems is 35 feet from the rear axle on your tandems to the last axle of your trailer tandems, you will have to reduce the amount of weight that you load onto your truck.
 
Here is the part of the bridge table that shows this:
Bridge Table Watch out for 35 foot mark

This means when axles 2 and 5 are 35’ apart (see picture below), you can only have about 32,750 lbs on your tractor tandems and your trailer tandems.
To avoid having this weight reduction, keep the distance between axles 2 and 5 at least 36 feet apart.

Semi Truck Figure Watch out for 35 foot mark

Issue number 2

Some jurisdictions restrict your truck to have a rear overhang that is “35% of the trailer wheelbase.” In these states you cannot have a short distance between your kingpin to your tandems, and then a long distance from your tandems to the end of your trailer. If you operate a typical 53’ van trailer, that has 3’ kingpin setback, then you cannot have the center of your tandem axles less than 37’1” from the kingpin.
Where does this apply?

  • Canada
  • Maine
  • Maryland
  • New Jersey

Semi Truck Figure 37 feet 1 inch for effective overhang