Curb weight is the total weight of a vehicle when it is full of fluids and ready to operate minus the weight of the driver and passengers. This measurement is used to determine tire specifications and, in many areas, license plate fees. Curb weight differs from gross weight in that gross weight not only includes the vehicle, all fluids being full and a driver, but it also demonstrates the weight of the vehicle when it is loaded to its maximum hauling capacity. It is used in determining what size of motorcycle a person can handle. Curb weight is also used to calculate vehicle shipping charges when having a vehicle delivered to a location by truck or ship.
The measurement can be an important factor in determining the weight capacity of a small aircraft. When deciding on the proper load limit of the airplane, the pilot can factor the curb weight of the plane and the weight of all passengers, then subtract the figure from the total gross load capacity of the aircraft. This will tell the pilot the total amount of luggage weight which can be loaded onto the aircraft without hindering its flight characteristics. This same formula can be applied to small watercraft as well.
When towing a vehicle on a trailer, the trailer capacity is mandated by the curb weight of the vehicle being towed. This is the only determining factor, since it is not legal to have passengers in a towed vehicle or a loaded vehicle on a trailer. To move a disabled vehicle such as a truck with a full payload, a wrecker must be used to safely tow the vehicle. The weight of the vehicle is added to the weight of the trailer to give the trailer's gross weight hauling capacity. This ensures proper braking abilities and proper tire wear while loaded.
Curb weight capacity is listed on many small recreational vehicles such as snowmobiles and off-road buggies. The weight limits must be factored in with the operator's weight to calculate gross vehicle weight numbers. These numbers are important due to many off-road bridges having light load capacities. The vehicle manufacturers cannot know the weight of the person who will purchase or ride the equipment; therefore, the company has given the rider the ability to do the math and arrive at each individual's gross weight factors. This enables the consumer to assure the proper level of safety when operating a recreational vehicle.