Many NTEA members receive requests from truck buyers to install bodies or equipment that would not leave the user enough cargo capacity to carry the intended equipment or cargo. Following a review of how to calculate axle weights published in the January issue of Light & Medium Duty Truck magazine, it seemed logical to review how to calculate a truck’s net cargo—the amount of cargo a truck can carry without exceeding the truck’s gross vehicle weight rating (GVWR) and gross axle weight rating(s) (GAWRs) issued by the chassis manufacturer.
The total vehicle weight including truck chassis, body / equipment, cargo and driver / passengers must not exceed the weight limit expressed in the GVWR that can be found on the vehicle’s certification label, usually located on the rear edge of the driver’s door or door jamb. A truck rated at 15,000 lbs. GVWR should not be operating at 16,000 lbs. Overloading causes safety issues such as exceeding the truck’s brake capabilities, leading to longer stopping distances, as well as causing accelerated wear and tear resulting in a shorter life cycle.
Determining cargo capacity is easy once you know the GVWR, body and / or equipment and chassis weights. Remember that a truck carries not only the cargo, but also its own empty weight, the weight of the body, passengers, fuel and any permanently installed equipment. Please be aware that cargo means different things to different people. The NTEA believes that using the following method provides operators with the best way to determine a vehicle’s true cargo capacity.
First, take the truck chassis’ curb weight (bare chassis weight), then add the weight of the truck body and / or equipment and that of the driver and passengers. You must allow 150 lbs. for each designated seating position (seat belt). Make sure that the chassis weight is a “wet weight,” meaning it includes a full tank(s) of fuel and all other necessary fluids and lubricants. Subtract the total unloaded vehicle weight (TUVW) from the truck’s GVWR, and you have the maximum net cargo (i.e., the amount of cargo the truck can carry).
Once you have the maximum net cargo, you must perform weight distribution to ensure that individual axle loads do not exceed the corresponding GAWRs as well as federal and state weight laws, regulations and restrictions. If the cargo exceeds any GAWR, the cargo must be reduced or use a chassis with a higher GVWR and GAWR.
The issue of overloading a truck can be touchy for many up-fitters (i.e., the final-stage manufacturers who build and install bodies and other equipment on new incomplete truck chassis). Although they are often asked to, they are not permitted to (and most reputable up-fitters will not) install equipment that when used as intended, would result in a truck exceeding the GVWR or GAWRs. If they do so, the National Highway Traffic Safety Administration (NHTSA) considers the installation a safety defect and holds the up-fitter liable for recall and remedy. If a final-stage manufacturer installs a body, such as a tank, of fixed size or volumetric capacity, it would cause the truck to exceed the GVWR when filled to its stated limit with the intended cargo it is designed to carry. Therefore constituting a safety defect, that could be the responsibility of the final-stage manufacturer to remedy, not the operator.
However, NHTSA recognizes that an operator can overload any truck. The following is from a NHTSA interpretation that addresses this issue, “NHTSA realizes that overloading is a problem created for the most part by the operator of a vehicle. Accordingly, it is not intended by the agency’s interpretation of regulations to hold a vehicle manufacturer responsible for every situation in which a vehicle is overloaded. Most any type truck can be overloaded by the user. An operator should be aware of this possibility, however, given the amount of space on that vehicle cargo can be loaded and the broad range of cargo that can be transported by that vehicle. If a truck designed for the transportation of one specific cargo were misused by the operator to transport another type of cargo not intended by the vehicle manufacturer, then any resultant overloading would be the responsibility of the operator not of the manufacturer.”
For these reasons, reputable up-fitters will take the time to work with the end user to ensure the chassis and body or equipment combination is going to meet customers’ cargo expectations. If you have questions, call the NTEA Technical Services Department toll-free at 1-800-441-NTEA. They’ll be glad to help
* Kleinstiver, Louis. “Payload Capacity: A Weighty Matter.” Truck Equipment News May 2002, a publication of the National Truck Equipment Association. Farmington Hills, MI. Page 2 and 7.