Specing body and chassis combinations

This article was published in the July 2015 edition of NTEA News

Question: As a truck equipment distributor, we routinely consult body charts published by chassis manufacturers to ensure we are installing appropriately sized bodies on our customers’ chassis. Sometimes, customers request bodies that are not included or are different lengths than in the chart. What should we do when this occurs?

Answer: These charts are intended to put you “in the ball park” when spec’ing a particular body and chassis combination. They are generally accurate to the degree that the assumptions and rules-of-thumb presented within apply to the upfit being evaluated (see references at the end of this article for available OEM body application charts). Whether a given truck body is included in one of the application charts or not, it’s important to perform a thorough weight distribution calculation when determining suitability of a body/chassis combination. The application charts help identify a range of typical body lengths for a particular chassis model/wheelbase/cab-to axle (CA) combination. They are also beneficial in distinguishing body applications requiring further evaluation. As mentioned, recommendations should not be taken as-is without performing your own weight distribution. 


The charts are primarily based on reasonable assumptions related to weight distribution (their fine print often reflects the presumptions that go into recommended body lengths). For the most part, the charts revolve around the tendency for a body — such as a flatbed or van body — to have its center of gravity located at the approximate horizontal mid-point. Another typical estimation is that cargo is loaded uniformly across the length, positioning its center of gravity at the same horizontal location as the body. A related industry dimension reflected in the application chart recommendations is a 3" cab-to-body clearance for chassis-cab models (note, this would not apply to other chassis upfits, such as stripped and cutaways). From the chassis dimensions, specifications and weight deductions, OEMs can work backward to arrive at body lengths recommended in the application charts. When taken together, this information can guide users to lengths that would reasonably distribute portions of body weight and cargo between the front and rear axles.


This is a good starting point, but is only as solid as the assumptions behind it. Even for a uniform body with evenly distributed cargo, having a piece of equipment, such as a generator, behind the cab would position the body and cargo centers of gravity further rearward, making a longer CA model necessary for proper weight distribution — which would not likely be reflected in a given application chart.


Additional guidelines
If a chart is not available for reference, another way to begin evaluating suitable body length for a given chassis is the general principle of having 60–70% of a uniform body length ahead of the center of the rear axle(s). This would position a body such that the centers of gravity of body and cargo are distributing weight to the front and rear axles. For example, take a percentage in this range and multiply by a given body length, then add cab-body clearance to ascertain CA dimension and begin further evaluation of available chassis. Using 60% of the length of an 8' body and 3" clearance would result in an approximate 60" CA. Use the same method to arrive at body lengths to pair with a particular CA if starting from a known chassis.


OEM application charts

  • Ford
  • GM
  • Hino


Assistance with weight distribution calculations is one of the many benefits members can take advantage of by calling NTEA’s Technical Services Department at 800-441-6832 from 8 a.m.–5 p.m. EDT, Monday–Friday.