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Axle Weight Limits Calculator By State | Steer, Drive, Single, Tandem, Tridem Axle Load Legal And Permitted Weight

Introduction

Every public road in the United States is governed by regulations concerning oversize/overweight vehicles at both the federal and state levels, all the way down to municipal levels in some cases. The ramifications of these regulations affect every aspect of our domestic and worldwide economies. Manufacturers must consider the size and weight limitations of their products to keep their transportation costs down, international exporters must consider the differences in freight regulations while crossing international borders, government entities must be able to calculate the damage to infrastructure by issuing overweight permits. Many years of research and planning have gone into the regulations that govern our public roadways and those charged with enforcing these regulations do not take that lightly. Violating these regulations could result in hefty fines or worse. These regulations are here to keep our infrastructure intact, maintain a safe and orderly roadway for everyone who uses it, and to provide a standard for our economy to establish itself upon. This examination will specifically pertain to axle weights and spacing regulations. It is important to note that these are not the only regulations governing oversize/overweight vehicles and it is strongly encouraged that readers investigate and familiarize themselves with all other regulations on all government levels.

Primary Considerations

There are several factors to consider before ever placing a load on a vehicle. These factors include: the dimensions of the load, the combined effect of the load and vehicle configuration, whether the equipment is rated to handle the dimensions of the load, if the dimensions are within regulation, etc. It is important to consider these factors ahead of time so that a proper plan can be made for transporting the load.

Axle and Equipment Regulations

Why are these regulations necessary to begin with? A look at the most basic algebra answers that question. Pressure is equal to force divided by area (P=F/A). Simply put: the more area that is there to spread the force out, the less severe the force becomes. In the illustration below, notice that the more axles and space added (more area) the more load weight (more force) is allowed on the truck and trailer.

Vehicles with axles

The most important factors that are heavily regulated concerning this principle are:

  • Axle Weight – the amount of weight allowed on any one axle or specific group of axles. Example: a legally dispersed 5 axle rig would have a max axle weight of 12000 lbs on steer, 34000 lbs on the drive tandem axles, 17000 lbs on the 4th axle, and 17000 lbs on the 5th axle.
  • Axle Spacings – the amount of space between axles, measured from the center of one axle hub to another. A standard 5 axle rig would be similar to 19-6 between the steer and first drive axle, 4-6 between the two drives, 35-0 between the last drive and the first trailer axle, and 4-6 between the two trailer axles.
  • Tire Width - the width of the tire. A state might say you are allowed 650 lbs per square inch of tire multiplied by the number of tires on that axle.
  • Manufacturer’s Rating – the specific tolerances that the tires and axles are rated to handle by the manufacturer.

Axle Weight Calculator

Oversize.io has accounted for every state’s specific rules and regulations. Simply input your vehicle configuration and select the states you are going through to see if your oversize load is permittable. You can change the weight distribution by changing each axle weight or axle spacing (if you have a slide axle trailer).


Axles weight calculator

Vehicle configuration

Federal Regulations

The following are the Federally mandated maximum weights for the National System of Interstate and Defense Highways and reasonable access thereto (23 CFR Part 658.17):

  • 80,000 pounds gross vehicle weight
  • 20,000 pounds single axle weight
  • 34,000 pounds tandem axle weights

Bridge Formula Weights - all loads traveling on the interstate roadways must comply with the Federal Bridge Formula.

The federal regulations state the maximum values listed above for a legal load. If a load violates these declared values, then the load requires a permit. The federal government itself does not issue permits for loads, but instead leaves it up to the state to decide if they want to allow the movement of loads.

State and Provinces Regulations By State

Every US state and Canadian province has its own regulations concerning oversize/overweight loads and must be researched. Each has available literature that it provides to help you make an informed decision about how to configure your equipment or disperse your load weight while traveling on their roadways. An example is the state of Texas. Texas will permit a single axle limit of 25,000 lbs on a single axle so long as the manufacturer’s ratings (GAWR) allow it. This knowledge of the state specific rules could help you get the extra weight you need to move a load.

Summary

Roadway regulations governing oversize/overweight loads can be a hassle, but they serve a very important purpose. They protect our infrastructure and provide a standard that effects domestic and worldwide economies. Axle weights, axle spacings, tire widths, and manufacturer’s ratings are the most important factors to consider. Each state has their own guidelines concerning each one of these factors. Oversize.io has considered all the state guidelines and done that research for you. Simply input your configuration into our system and receive immediate feedback on whether your load meets state and federal guidelines. Don’t hesitate to contact us with any further questions.


Cited References

https://ops.fhwa.dot.gov/freight/sw/permit_report/index.htm

More Information

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