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October 12, 2022
Let’s talk vehicle capabilities, in terms of weight and how much it can carry. Whether it’s a UTV, pick-up truck or full-size fire truck, they all have five calculations and ratings that define how much weight the vehicle can carry: GVWR, GCWR, GAWR, Curb Weight, and Payload. Bed capacity also factors into this, but in general, the first five form the basis of the carrying capacity of the vehicle.
Let’s look at each rating:
GVWR stands for Gross Vehicle Weight Rating, and is the maximum total combined weight of the vehicle, including passengers, cargo, fuel, tongue weight (if towing) and all other items.
GCWR stands for Gross Combined Vehicle Weight Rating. This is the maximum total combined weight of both the vehicle and trailer.
GAWR is Gross Axle Weight Rating – the maximum weight either axle can carry individually – and there will be a different rating for both the front and rear axles.
Curb Weight is the weight of the vehicle in its running state, complete with oil and fuel, but without any passengers or cargo.
Payload is how much weight the vehicle can carry.
Now let’s take a look at how we arrive at some of these numbers.
GVWR is set from the factory, and will vary depending on suspension and wheel options. A bare-bones, SRW (Single Rear Wheel) Ford F-350may have a GVWR of 10,000 pounds, but can be optioned with an upgraded GVWR of11,400 pounds.
GCWR is also set from the factory, and is determined by combining the vehicle’s curb weight, payload and trailer weight. GCWR is the combined maximum weight limit of both the drive chassis and the tow vehicle once the two are attached.
GAWR is the listed weight is the maximum load each axle can carry, and this number can be determined by weighing the front end and rear end of the vehicle separately once fully loaded with fuel, passengers and cargo. Oftentimes, if you add up the combination of front and rear GAWR, the total weigh will be more than the GVWR of the vehicle. This is because some manufacturers build a margin into the axle ratings to ensure they’re not overloaded when the vehicle is within its specified operating range.
Here are some examples.
Let’s say you want to determine the payload of your vehicle. The calculation is:
GVWR - Curb Weight = Payload
If your vehicle has a 10,000-pound GVWR and a curb weight of 6,000 pounds, your maximum payload is 4,000 pounds. If we were trying to determine how big of a firefighting skid the truck should hold, we’d have to make some assumptions and also look at the bed capacity. The bed capacity can’t be the total payload, because manufacturers have to account for passengers and other cargo.
For example, let’s assume the truck has a 2,500 pound bed capacity. Water is 8.34 pounds per gallon, so a 250 gallon firefighting skid will have 2,085 pounds of water on board. That means the weight of the skid itself – the tank, pump and plumbing, without water – can’t be more than approximately 400 pounds.
Vehicle weight ratings are one of the most important considerations when building up a fire truck or UTV. Safety must be paramount, so don’t overload a vehicle, regardless of its mission and how much you’re trying to accomplish with it. Always stay within the limitations of a truck or UTV's design parameters.
If you need to haul more weight, get a bigger truck.