Motorhome Basics | FMCA
You've probably heard it said that a chain is only as strong as its weakest link. This theory applies to motorhome chassis as well.
The chassis manufacturer establishes weight ratings and limitations based on the major components of the system — the engine, transmission, brakes, axles, tires and frame. These components are designed to accommodate a particular weight, and if they are overloaded, their life expectancy diminishes rapidly.
So, it is important for motorhome owners to understand the various weight definitions used by motorhome and chassis manufacturers. Of course, the next step is to have your motorhome weighed after you have loaded it for travel to make sure it falls within the various ratings.
GVWR (gross vehicle weight rating): the maximum permissible weight of the fully loaded motorhome, including liquids, passengers and cargo. The GVWR is equal to or greater than the sum of the unloaded vehicle weight (UVW) plus the net carrying capacity (NCC).
GCWR (gross combination weight rating): the value specified by the motorhome manufacturer as the maximum allowable combined weight of the motorhome and the attached towed vehicle.
GAWR (gross axle weight rating): the maximum allowable weight each axle assembly is designed to carry, as measured at the tires, including the weight of the assembly itself. GAWR is established by considering the rating of each of its components (tires, wheels, springs and axle) and rating the axle on its weakest link. The GAWR assumes that the load is equal on each side of the vehicle.
RVIA weight label
In September 1996, the Recreation Vehicle Industry Association (RVIA) established a requirement for its RV manufacturer members to disclose weight carrying information that would assist both a buyer and an owner in understanding and complying with weight limitations of motorhomes. The following terms and their associated weights are reflected on a label, found in a cabinet inside the coach.
UVW (unloaded vehicle weight): the weight of the motorhme as built at the factory with full fuel, engine oil and coolants. The UVW does NOT include cargo, fresh water, LP gas, occupants or dealer-installed accessories.
NCC (net carrying capacity): the maximum weight of all occupants including the driver, food, tools, LP gas, fresh water, personal belongings, dealer-installed accessories, and the tongue weight of the towed vehicle that can be carried by this motorhome. (NCC can be determined by subtracting the UVW from the GVWR.)
It's important to look at the definition of each term, particularly the UVW and NCC. Note that UVW is defined as leaving the factory with full fuel, oil and coolants. The NCC represents how much "stuff," including fresh water, the motorhome can carry.
The UVW does not include the weight of any dealer-installed accessories, which means the buyer must deduct the weight of these accessories from the NCC.
Keep in mind that NCC is the total carrying capacity. However, the distribution of the weight plays a role. So, it may not be possible to load a motorhome to its NCC without exceeding an axle or tire rating. Weighing your motorhome by individual wheel position after you have loaded it is the only way to be certain that you are not exceeding any limitations.
In September 2000, the RVIA modified the label to provide more detail for the buyer/owner. The term NCC is no longer used. Two new terms are found on the label, along with their associated weights:
SCWR (sleeping capacity weight rating): the manufacturer’s designated number of sleeping positions multiplied by 154 pounds (70 kilograms).
CCC (cargo carrying capacity): the GVWR minus each of the following: UVW, full fresh (potable) water weight (including water heater), full LP-gas weight, and SCWR.
This new label permits the buyer/owner to determine the carrying capacity (CCC) based on a personal calculation of actual passengers carried, the amount of fresh water onboard, and the amount of LP-gas carried.
Use the RVIA label as a guide to narrow your selection of vehicles, but keep in mind its limitations.
This information was provided by A'Weigh We Go, a national weight safety program that is now a service of the Recreation Vehicle Safety Education Foundation (RVSEF). The Foundation sponsors nine RV safety programs and conducts educational seminars.