Over the years, there have been strides made in standardizing RV vehicle weight definitions, through the efforts of the Recreational Vehicles Industry Association (RVIA), RV Dealer’s Association (RVDA) and RV Safety Education Foundation (RVSEF).
Note that manufacturers of trucks used to tow trailers fall outside of the realm of the RVIA, so you should always check specific manufacturer guides and manuals to understand vehicle weight definitions used.
Do the math for your specific RV and tow vehicle, and make sure you know what is included (or not included) in any numbers you get from a manufacturer, private owner, or dealer. The main thing is to account for all weight and weight distribution in selecting and using your RV, tow vehicle and hitch mechanisms.
Vehicle Weight and Rating Terminology:
Note the difference between “ratings” and “weights/loads”:
- Ratings cannot be changed – they are maximum allowable limits determined by the manufacturer in the design of the vehicle.
- Weight and load are generally used interchangeably. In RV applications, vehicles have weight, which imparts loads to tires, axles, and hitches. Scale measurements taken when weighing are loads carried by the tires. These measured loads are used to calculate Gross Vehicle Weight (GVW), Gross Axle Weight (GAW), Gross Combination Weight (GCW), and hitch loads.
GVWR (Gross Vehicle Weight Rating) means the maximum allowable weight of the fully loaded vehicle, including liquids, passengers, cargo and the tongue weight of any towed vehicle. Note: The tow vehicle and RV each have a GVWR.
GAWR (Gross Axle Weight Rating) is the maximum allowable weight each axle assembly is designed to carry, as measured at the tires, including the weight of the axle assembly itself. The GAWR is specified by the vehicle manufacturer. It is established by considering the rating of each of its components (tires, wheels, springs, axle), and rating the axle on its weakest link.
The GAWR assumes that the load is equal on each side. This is a rating of the maximums for an axle. It is possible to be overloaded on one end of the axle, and still not exceed the GAWR – hence the recommendation that you obtain individual wheel position weight measurements and inflate tires according to the load.
GCWR (Gross Combination Weight Rating) is the maximum allowable combined weight of the tow vehicle and the attached towed vehicle. GCWR assumes that both vehicles have functioning brakes, with exceptions in some cases for very light towed vehicles (less than 1,500 lbs). Check your chassis manual or manufacturer towing guide.
UVW (Unloaded Vehicle Weight) is the weight of the unit as built at the factory. with full fuel tanks, engine oil and coolants. The UVW does not include cargo, fresh water, LP gas, occupants or dealer-installed accessories.
NCC (Net Carrying Capacity), used from 1996 – 2000, is the maximum weight of all personal belongings food, fresh water, LP gas, tools, dealer-installed accessories and other items that can be carried by the unit.
CCC (Cargo Carrying Capacity), used Sept 2000 – present, means GVWR minus the following: UVW, full fresh (potable) water weight (including that for the water heater) full LP gas weight, and SCWR. Note: Remember that optional accessories or equipment not included in the UVW will take up part of the Cargo Carrying Capacity.
SCWR (Sleeping Capacity Weight Rating) is the manufacturer–designated number of sleeping positions multiplied by 154 lbs (70 kgs).
Example of Cargo Carrying Capacity computation on a Motorhome Vehicle Weight Information plate:
GVWR 22,000 lbs.
Less UVW – 16,000 lbs.
Less 20 Gallons Fresh Water x 8.3 lbs. Each – 166 lbs.
Less 16 Gallons Propane x 4.5 lbs. Each – 72 lbs.
Less SCWR (4 x 154 lbs.) – 616 lbs.
Cargo Carrying Capacity (CCC) – 5,146 lbs.
GVW (Gross Vehicle Weight) is not a limit or specification. It is obtained when the fully loaded vehicle is driven onto a scale. The Gross Vehicle Weight, should not exceed the Gross Vehicle Weight Rating (GVWR) or the vehicle’s warranty could be voided. Refer to the owner’s guide for the specific vehicle.
GTW (Gross Trailer Weight), often used in towable RV applications, this is the same concept as GVW. Gross Trailer Weight, including tongue load or king pin weight, is measured by putting the trailer on a scale.
GAW (Gross Axle Weight) is the weight of a fully loaded vehicle that is supported by a single axle, obtained by weighing the vehicle on a scale.
GCW (Gross Combination Weight) is the combined weight of the fully loaded vehicles, as measured on a scale.
Hitch Ratings: Hitches are rated by the manufacturer, so always check the manufacturer specifications. Trailer hitches have Gross Trailer Weight ratings, for the maximum towed vehicle weight allowed. Each component (receiver, drawbar and ball) of a ball-type hitch has its own rating. A ball is rated by its towing capacity. A hitch is rated by its towing capacity but also by the tongue weight. Some ball-type hitches have separate ratings when used with a weight distributing system.
Use the hitch rating in conjunction with the actual towing capacity of the towing vehicle. The maximum towing capacity of a vehicle is determined by the lowest-rated element in the chain of hitch components.
- For trailer towing, this chain consists of the trailer rating, the ball hitch rating, the hitch rating, and the towing capacity of the vehicle. The weakest, or lowest-rated, element in this chain always determines the maximum safe towing capability of the entire chain.
- For the motorhome towing a dinghy, consider the towing capacity of the motorhome itself, as well as the ratings for a tow bar and associated cables, base plates and connector.
TWR/TLR,VLR (Tongue Weight, Tongue Load, Vertical Load Rating): These tow ratings are different terms for the maximum vertical load that can be carried by the hitch. Tongue weight measurements should be made before towing. Tongue weight, or king pin weight for fifth wheel trailers, refers to amount of the trailer’s weight that presses down on the trailer hitch.
Too much tongue weight can press the tow vehicle down in back, causing the front wheels to lift to the point where traction, steering response and braking are severely decreased. Suspension or drivetrain damage can result.
Too little tongue weight can reduce rear-wheel traction and cause instability, swaying or jackknifing.
For proper handling, tongue loads should be:
- For trailers up to 2,000 lbs., not to exceed 200 lbs.
- For trailers over 2,000 lbs., 10 – 15% of trailer weight.
- For fifth-wheel trailers, 15% to 25% of trailer weight.
For example: For a 5,000-lb. trailer, multiply 5,000 by .10 and .15 to obtain a proper tongue load range of 500 to 750 lbs.
For an 11,500-lb. fifthwheel trailer, multiplying 11,500 by .15 and .25 yields a king pin weight range of 1,725 to 2,875 lbs.
Tongue load is measured by disconnecting the trailer and placing only the tongue – with the coupler at hitch ball height – on a scale.
If the tongue load exceeds the upper weight limit, move more of the trailer contents toward the rear to achieve the recommended tongue load.
If the tongue load is less than the lower limit, shift the load forward. Weight should also be balanced right to left and secured in place.
LIQUID WEIGHTS (pounds per gallon)
- Water: 8.3
- Gasoline: 5.6
- Diesel Fuel: 6.8
- Propane: 4.2
The RVIA does not regulate truck manufacturers, so you may see variations in vehicle weight definitions used. Just be sure you understand how the definitions are being used by a specific manufacturer. Here are a few terms you are apt to see for trucks that can tow trailers:
Dry Weight/Wet Weight/Curb Weight: Dry Weight is normally used to refer to the empty weight of the vehicle or trailer.
Curb Weight or Wet Weight definitions generally refer to the vehicle weight including standard equipment, oil, lubricants and a full tank of fuel. It does not include optional contents or other optional equipment, the weight of driver, passengers or cargo. Sometimes, but not always, it includes fresh water and LP.
Yikes! Just make sure you get the written definition of what’s included from whoever has given you the numbers.
Payload: Payload capacities generally are computed by subtracting the curb weight of the vehicle from its specified Gross Vehicle Weight Rating (GVWR). The addition of any optional equipment or passengers adds to the vehicle weight and subtracts from the allowable payload.