Vehicle specifications should be defined by the fleet application and mission requirements. It is important to design a truck that will accommodate your operational requirements rather than trying to make your operation conform to the truck. A common mistake made by inexperienced fleet managers is that they do not know the truck’s operating parameters and payload requirements. You need to talk with the people in the field to understand what type of service the truck is expected to perform and how it will be used.
By determining the fleet application, you will determine the payload. The most important factor in truck selection is determining the payload needed to perform a particular operation. Overextending a truck’s payload capacity beyond the chassis’ weight specifications is a good way to shorten the truck’s service life.
Determining Payload Requirements
There are three components to determining payload requirement. The first is payload weight. How much weight will the truck need to carry in its daily workload? You need to determine the maximum need, not an average. The vehicle must be able to do the job every day with the maximum load at any given time. Payload weight will also help determine if the cargo can be loaded and unloaded by hand, or whether you will need a power lift gate or some other type of assist to get it up in the body or bed.
Another area is in the volume or size of the payload. The truck needs to be large enough to handle the volume. And, you need to know how the payload will be loaded. Is it stackable? Can you stack it right to the ceiling? Or, can only the floor space be used? How do you secure the product? Getting any of these factors wrong can mean the vehicle will be spec’ed incorrectly.
The third component is the type of payload. Are you hauling loose gravel, pallets, or boxes of merchandise? This will determine the type of truck and body combination you need to choose.
The best way to determine actual payload is to take a normally loaded truck and weigh it on a highway scale. Another practical tip is to weigh the front and rear axle. This will tell you if you are overloading the whole truck or just one of the axles.
Overloaded trucks will cause premature tire wear, decreased fuel economy, and downtime due to engine or transmission repair. In addition, overloading results in fines and possible impoundment of the vehicle by the authorities.
You need to make sure that the truck can carry not only the payload but also any additional equipment you put on the truck. The fleet manager needs to add the body and equipment weight to that of any tools or other material that could be stored or transported by the chassis.
There is a tendency to under-spec trucks to avoid exceeding the 26,000-lbs.-GVW threshold, which requires drivers with commercial driver’s licenses (CDL) and regulatory compliance. When spec’ing a smaller GVWR truck than required, the tendency is to overload the vehicle. Besides accelerating replacement of wear items, such as brakes, an overloaded vehicle also increases the company’s liability exposure if it is involved in a preventable accident. There are other potential ramifications that may result from this, including the requirement for multiple trips due to limited payload capacity.
Importance of Reserve GVW
To determine the correct vehicle size for the intended payload often requires a judgment call as to how much over-capacity to build into the payload capacity of the vehicle when spec’ing its requirements. Spec’ing the truck to the minimum necessary payload rating (by basing it on an average load or looking at only today’s business needs instead of trying to anticipate future needs) means that the vehicle will be operating at peak capacity most of the time, which may compromise safety and the length of its service life. Using average payload for specs means that the vehicle will sometimes be overloaded – and that means excessive wear-and-tear, higher maintenance costs, and poor fuel economy. Conversely, too much payload capacity is wasted capacity.
One of the most common mistakes is not allowing reserve GVW when spec’ing a truck. Your objective is to select a truck that offers a slight buffer in payload capacity without overkill, which would unnecessarily drive up costs. Generally speaking, there should be approximately 20-percent reserve GVWR.
Building a truck is a complicated process. Specifying the right truck requires hundreds of decisions and choices – and each choice potentially impacts another. The tricky part is finding the balance between over-spec’ing and under-spec’ing a vehicle, each with its own unique set of consequences. Over-spec’ing a truck increases the capitalized cost of the vehicle, while under-spec’ing increases maintenance cost.
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