Trucks come in a variety of weight capabilities. Use of a simple formula can assist fleet managers in selecting the right chassis components when net payload is reduced by the addition of an upfitted body, racks, and other equipment.
 - Image coutesy of General Motors

Trucks come in a variety of weight capabilities. Use of a simple formula can assist fleet managers in selecting the right chassis components when net payload is reduced by the addition of an upfitted body, racks, and other equipment.

Image coutesy of General Motors

Fairytales are hard to shake and can be misleading. Light truck designations of 1/2-ton, 3/4-ton, and 1-ton are still in use despite having little relevance to payloads and capability.

When a truck leaves the factory, there is little question about what it is rated to carry — the gross vehicle weight rating (GVWR) appears on the plate attached permanently to the vehicle. GVWR, however, includes everything: truck chassis, body, driver weight, all fluids topped off, spare tire, aftermarket upfittings, glove box contents, and net payload.

Net payload isn’t shown separately. In fact, some manufacturers refer to “payload” as including a body installed by somebody else on chassis-cab models.

It is suggested the use of a simple formula to determine net payload capacity after allowing for everything installed on a truck. The formula was published for NTEA members to use when installing bodies and equipment to customer chassis, but it can also be used by fleet managers to specify new equipment. 

CHART 1

Selection of a Full-Size 125-Inch Wheelbase Truck 1/2-ton 1/2-ton 3/4-Ton 1-Ton 1-Ton
  Base Max Base Base Max
Vehicle GVWR (lbs.) 4,900 6,000 6,600 7,100 8,600
Curb Weight (lbs.) with all the factory options 4,144 4,181 4,223 4,734 4,854
Upfitted Materials (lbs.) 780 780 780 780 780
Completed Vehicle Curb Weight (lbs.) 4,924 4,961 5,003 5,514 5,634
Driver and Passenger (lbs.) 300 300 300 300 300
Total Vehicle Weight (lbs.) (including passengers) 5,224 5,561 5,303 5,814 5,934
Maximum Net Payload (lbs.) -324 730 1,297 1,286 2,666

 

Once the maximum net payload is determined, a weight distribution must be calculated to determine that the manufacturer’s gross axle weight ratings (GAWR) are not exceeded. These ratings are shown on the manufacturer’s plate affixed to the vehicle, and they also appear in truck data books.

When using this formula, factory data books are the best source for chassis and factory option weights, but be sure to allow 150 lbs. for each occupant provided with a seat belt. (Sometimes factories include occupants in option and chassis weights.) Also, supplier catalogs often publish body and body option weights.Using the example of a Class 2 truck in Chart 1, payload capacity would be reduced by 1,200 lbs. of body and body options added after the chassis was produced.

The GAWR is determined by the lowest-rated capacity of the tires, brakes, wheels, suspension, and axle assembly. When fully loaded, the weight of the completed vehicle must not exceed the GVWR, and the weight must be distributed so that the GAWR of each axle is not exceeded.

HOW TO CALCULATE MAXIMUM NET PAYLOAD

Chassis-Cab GVWR
=10,000 lbs.

Chassis Curb Weight with All Options
+ 4,200 lbs.

Body and Equipment Weight
+ 1, 200 lbs.

Completed Vehicle Cub Weight
= 5,400 lbs.

Driver and Passengers (150 lbs. each)
+450 lbs.

Total Vehicle (Including passengers)
= 5,850 lbs.

Maximum Net Payload
(10,000 lbs.-5,850 lbs.)
= 4,150lbs.
 

How to Select the Right Van

The equation illustrates how a fleet manager can use the NTEA formula for selecting the right van chassis for several alternatives of a popular 125-inch wheelbase van. These vans are offered as several models and GVW may often be boosted with heavy-duty options for each model.

Each vehicle was equipped with recommended aftermarket bins and shelving for a plumbing and heating contractor, provided a roof carrier for conduits, a storage box for the driver, and included a passenger seat. Also included were a spare tire and wheel and a larger than standard fuel tank. The only comfort added was air conditioning. All vehicles are base sizes, except the V-8 maximum one-ton version.

According to the chart, the base 1/2-ton model would be overloaded before any cargo was added and a maximum spec 6,000 lb. 1/2-ton would have a net capacity of only 730-lbs. — too little to be of much value to a plumber. If the user could live with just under 1,300- lbs. net payload, then either a 6,600-lb. GVW 3/4-ton or a 7,000- lb. GVW one-ton could do the job. (Fleet managers usually know what kind of load they carry).

Maybe 1,300 lbs. is inadequate, in which case, the best option is the 8,600-lbs. 1-ton version, with a maximum net payload of 2,666 lbs. If that isn’t enough payload, other types of vehicles should be considered, such as, a van cutaway with dual rear wheels, a forward-control chassis, or perhaps a chassis-cab Class 3 and Class 4 truck with aftermarket body.


RELATED: How to Avoid Over- and Under-Spec'ing Pitfalls

0 Comments