Spec’ing a truck is a complicated process. Building the right truck requires hundreds of decisions and choices – and each choice potentially impacts another. Where it gets tricky is finding the balance between over-spec’ing and under-spec’ing a truck, 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 costs. With under-spec’ed trucks, there is a tendency by users to overload the vehicle. Besides accelerating replacement of wear items, such as brakes, an over-loaded vehicle also increases the company’s liability exposure if it is involved in a preventable accident.
Build the Truck to Match the Application
Specifications should be defined by the application and mission requirements. Trucks must be equipped to handle very specific fleet applications, which require specifying a multitude of components such as the right drivetrain, suspension, and body. By understanding day-to-day fleet applications, you will be able to build a truck that meets the users’ daily needs. Without fully understanding the fleet application requirements and operating parameters, it is impossible to spec the best chassis, powertrain, and body necessary to optimize productivity.
Fleet managers must understand how company trucks are intended to be used in the field; however, it is important to be aware that intended usage often does not match real-world usage. Look at the existing trucks in service and investigate the maintenance records. What type of problems has these trucks had, if any? This will help you determine if the current vehicles are under-spec’ed. If they are, then take the necessary steps to correct it. Usually, the majority of trucks that have unscheduled maintenance problems are under-powered and overloaded, which, in addition to increased shop time, results in increased driver downtime.
The most important first step to correctly spec’ing a truck is to meet and talk with the drivers or technicians who will be using the truck. This understanding will influence all truck specifications. It can’t be stressed enough that vehicle specifications must be defined by the fleet application and mission requirements. In the final analysis, it is critical to spec a truck that will accommodate its operational requirements rather than trying to make your operation conform to the truck.
When spec’ing a medium-duty truck, there are a number of key factors that must be spec’ed correctly. If not, you’ll end up making an expensive mistake.
Payload is the foremost consideration to properly spec’ing a truck. Again, it can’t be stressed enough that payload is the most critical aspect of truck spec’ing. To illustrate this fact, the weight of the payload will determine the engine, transmission, size of tire, frame, and just about everything else. The first step in calculating payload is to determine how much weight a truck will need to carry in its daily work application. It is important to determine the maximum need here, not an average. The vehicle must be able to do the job every day with the maximum load at any given time.
The best way to determine actual payload is to take a truck as it would be normally loaded and weigh it on a highway scale. Another practical tip is to also weigh the front axle and rear axle. This will tell you if you are overloading the whole truck or just one of the axles. You need to make sure that the truck can carry not only the payload but also any additional equipment you put on the truck. For instance, factor in the body and equipment weight, along with any tools or other material that may be stored or transported by the chassis.
Allow for 20 Percent GVW Reserve Capacity
To determine the correct size of a chassis for the intended payload often requires a non-scientific judgment call: namely, 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. At the same time, too much payload capacity is wasted capacity that should be avoided. One of the most common mistakes made by fleet managers is not understanding the importance of allowing reserve GVW when spec’ing a truck. Some items to consider when determining how much reserve GVWR is necessary include the wheelbase, axle rating, the type of body, and the type of application. Generally speaking, there should be approximately 20 percent reserve GVWR.
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