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Methods Of Weight Transfer

To make sure we have the terminology straight, refer to the following diagram:

• #1 Steer axle
• #2 and #3 together are your tractor drive tandem axles
  (commonly referred to as "drives" or "drive axles")
• #4 and #5 together are your trailer tandem axles
  (commonly referred to as "tandems" or "trailer tandems")

There are several ways to distribute the overall weight of the vehicle across the different sets of axles. You will affect weight distribution by:

• Changing the weight distribution of the cargo along the length of the trailer, or moving the cargo around after loading the truth. This will distribute the weight mainly between your drive axles and trailer tandems
• Sliding your trailer tandems forward or backward will redistribute the weight mainly between your drive axles and trailer tandems
• Sliding your 5th wheel will redistribute the weight mainly between your steer axle and your drive axles
• Adding or burning off fuel will mainly change the amount of weight on your steer axle and somewhat on your drive axles also, depending upon the placement of your fuel tanks.

Limitations On Weight Transfer

There are several factors that will reduce the amount of weight we can transfer between the different sets of axles on the truck:

• Federal laws limit the maximum weight on any set of axles and the gross vehicle weight - 20,000 pounds single axle, 34,000 pound tandem axles, 80,000 pounds GVW
• The bridge law formula limits the maximum amount of weight you can carry across any set of axles based upon the number of axles and the spacing between them (we'll discuss this formula soon).
• The maximum legal length allowed between your trailer kingpin and your trailer tandems will limit how far back you can slide your tandems
• The load rating of the tires you have will determine the maximum amount of weight allowed on any particular tire
• The load rating of the suspension system will limit the amount of weight you can have on any axle

The Most Restrictive Rule Always Applies

When distributing weight across a set of axles, the most restrictive law will ultimately be the limit for any situation. For instance, if the law states that you can carry 20,000 pounds on your steer axle, but your steer tires have a load rating of 6000 pounds each, then you can only carry a total of 12,000 pounds on your steer axle.

Another example would be a situation where you have 35,000 pounds on your trailer tandems, but only 28,000 pounds on your drive axles. Even though you may be able to slide your trailer tandems back far enough to get the weight distribution legal across all axles, if you have to slide them back beyond the legal limit allowed from trailer kingpin to trailer tandems, you will still be illegal. The weight distribution of the load itself would have to be changed in order to get your truck legal in this circumstance.

So you must comply with all the various laws in order to be legal on the highway. We will cover a variety of different scenarios throughout the rest of this section.