Motorhome Basics | FMCA
The first time to weigh your motorhome is even before you finalize the purchase. That way you can determine whether the vehicle will meet your needs in terms of carrying capacity.
Weigh before you pay
When purchasing a motorhome, you may not find a place to weigh your motorhome wheel by wheel, as weighing experts recommend. However, you can weigh each axle. Then, you can evaluate the placement of storage areas, liquid tanks, major appliances, slideouts, generator, LP-gas tank, etc. to see whether the distribution of these heavy components could cause problems. If the capacity is not reasonably distributed, you may have difficulty loading the coach within its limits.
When buying or weighing a coach, you must have a good knowledge of your personal weight carrying requirements. To help in your calculations, here are the approximate weights (pounds per gallon) of the liquids motorhomes can carry: water — 8.3; gasoline — 6; diesel fuel — 6.6; propane — 4.2.
When determining your requirements, keep in mind that everything you put in the RV has weight. We know from our weighing program that the average couple carries approximately 2,000 pounds of "stuff," and many full-timing couples may carry as much as 3,000 pounds.
Weighing your motorhome is critical to ensuring that no ratings limitations are exceeded.
Weighing by wheel position
Ideally, you will weigh the motorhome by individual wheel position. Considering the multitude of floor plans, slideouts, generators, holding tanks and the location of storage space available, RVs are frequently severely biased to one corner or one axle.
If you weigh your RV on a truck scale by axle and find that the vehicle is within GVWR, it could be that the vehicle exceeds a tire rating, especially if the GAWR is equal to the sum of the tire ratings, which is frequently the case.
Use a certified scale
To weigh your vehicle by individual wheel position, we suggest you use a certified scale. "Certified" means that a qualifying agency inspects the scale periodically to verify its accuracy. Most truck stop scales are certified, as are most grain elevators, co-ops, and other scales used in various trades.
The key is to find a scale that permits you to place individual wheel positions on the scale independently, while keeping the vehicle level and all wheels in the same plane. It is not critical to have the wheel in a particular position on the scale, and do not be concerned with what portion of the motorhome is on the scale and what portion is not. The individual wheel loads will be the same regardless of your position on the scale, as long as you keep the vehicle level.
Determining the loads
When weighing a motorhome in this manner, first determine the individual wheel loads, then calculate the axle loads and the actual gross vehicle weight. Add the wheel loads for each axle and compare the total to the GAWR for that axle. If the total is greater than the GAWR, then you exceed this rating. If the total is at or near the GAWR, a tire overload is probably.
Now, add all of the wheel loads together and compare that total to the GVWR for your coach. If the total exceeds the GVWR, then you exceed that rating.
Be sure to compare your wheel loads to the ratings of your tires. Remember that tire ratings vary with inflation pressure. If you discover a tire overload, resolve it immediately. Knowledge of tire load and inflation ratings can improve tire performance — and prevent accidents.
Towed vehicle weight
f you tow a vehicle behind your motorhome, determine its weight and compare it to the tow rating of your hitch system. Also, compare the total weight of your motorhome and towed vehicle to the GCWR for your coach.
If you tow a trailer or another vehicle that imparts vertical load to your coach, you will want to verify that this hitch load does not exceed the vertical load rating of your hitch.
Also, keep in mind that many chassis manufacturers specify that if a vehicle exceeding a certain weight is to be towed, supplemental braking for the towed vehicle is required; so, check with the chassis manufacturer.
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 RV safety programs and conducts educational seminars.