Commercial vehicle weight laws are the same from state to state when speaking about the standard truck and trailer.
Commercial Vehicle Weight Laws
This diagram shows axle #1, the steer axle as a maximum load of 12,000 pounds. This is true on most over the road tractors. By law you may have a maximum weight rating of 20,000 pounds on a single axle if the tires are rated for 20,000 pounds. 12.000 pound steer tires get much better fuel mileage so they are the typical choice of general freight haulers.
Axle groups 2,3 and 4,5 are allowed a maximum of 34,000 pounds because of there close grouping, known as tandems. Trailer tandem axles can be slid forward or backward to adjust weight.
Above you will see a trailer with what is called spread axles or split tandems. They are exactly 10′ 1″ apart and you are allowed 20,000 pounds per single axle. You will find that most flatbed and some reefer trailers have spread axles. The advantage is that very heavy loads do not stress the trailer as much as if you had tandem axles and load placement is not as critical.
The disadvantage of spread axle trailers is that they are much harder to turn sharply and back up because the front trailer axle tend to “drag” rather than pivot. All states commercial vehicle laws prohibit weighing more than 80,000 pounds, what is called gross weight.