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Weight and Capacities
An RV isn't quite the same as your typical automobile. There's a lot more size and weight to move down the road. All this extra weight and bulk creates heavier loads and stresses on the various components that make up the RV. Accordingly, there are limits placed upon just what you can and cannot do with each RV. Just as your basic Boeing 747 can't do aerobatic maneuvers without the wings falling off, you also can't do certain things - such as stop on a dime or haul more load than you are rated for. RVs have a number of weight ratings that are standardized throughout the industry but they can be confusing because there's so many of them. Lets take a look at what they are:
GVWR:
The Gross Vehicle Weight Rating represents just how much total weight the entire RV can weigh, if you parked it on a scale. When fully loaded the RV cannot exceed this number or else it is overweight and undue stress will be put on the chassis, engine, tires, etc. This number will vary from 18,000 lbs on the lightest class As up to around 45,000 lbs on a 45' Zephyr. If you fully load your RV and exceed this number you either have to put your RV on a diet and shed some of the cargo or else look for an RV with more capacity. Note that carrying capacity is not necessarily related to the GVWR. Some RVs have tons of bells and whistles, hardwood cabinetry, ceramic tile, and other heavy "stuff" built in so that there isn't much room for any cargo carrying ability while some lighter RVs may have plenty of cargo capacity simply because they were built lighter.
GCWR:
The Gross Combination Weight Rating is similar to the GVWR except it also counts any trailer or tow vehicle that you may have. You may have your coach loaded underneath the GVWR but if you try to pull a bulldozer behind it you'll definitely exceed the GCWR and won't be able to stop or accelerate without damaging your chassis or engine. If you have a 22,000 lb GVWR and a 26,000 lb GCWR you would be capable of towing a 4,000 lb vehicle "if" your RV was loaded to the full GVWR. If you were only loaded to 21,000 lbs, then you would have that extra room available for towing so you could tow a 5,000 lb vehicle. Note that the GCWR does assume that you will have tow brakes on any trailer or towed vehicle over 1,500 lbs.
GAWR:
The Gross Axle Weight Rating is a per axle rating so you will have one for each axle. When you weigh your RV you may be underneath your GVWR but if there is too much weight on one axle and not enough on the other, you'll be in for problems. The weight needs to be fairly evenly distributed so you'll have to shift cargo from front to rear or vice versa. If you add the two axle ratings up you may find that they add up to more than the GVWR so you have some room to play with when distributing the cargo but you still cannot exceed the GVWR. If you did excessively overload one axle you would find that the tires would be overstressed on that axle. You can also get some pretty squirrelly handling when there's not enough weight on the front or heavy steering if there's too much. A common misconception amongst RVers is to weigh the coach and load to the GVWR. However, if all this weight is placed on one end of the cioach, that axle will be overloaded while the axle on the other end of the coach will be under utilized. This is a common issue with large single axle coaches, such as 40' diesel pushers, that are loaded up with all the bells and whistles. The vast majority of that weight rests on the rear axle and that axle gets overloaded before the GVWR is ever reached. This effectively reduces the amnount of cargo you can carry to an amount lower than the GVWR unless you can shift some of that weight forward to the front axle.
UVW:
The Unloaded Vehicle Weight is the empty weight of the RV as it leaves the factory with full fuel tank, full engine oil and coolant. There is no propane, water, cargo, or occupants in this measurement.
NCC (1996 RVIA Definition):
The Net Carrying Capacity is the maximum weight of all cargo, fresh water, propane, dealer installed accessories, and passengers that can be carried by the RV.
SCWR (2000 RVIA Definition):
The Sleeping Capacity Weight Rating is the designated number of sleeping positions multiplied by 154 lbs.
CCC:
The Cargo Carrying Capacity is equal to the GVWR minus the UVW, minus the SCWR, minus the full fresh water tank and water heater water weight, minus the weight of a full propane tank. It represents what you can actually "pack" into the RV after every single tank is topped off and loaded with 154 lb. passengers (one per sleeping position).
Note that for the above calculations you can use the following numbers when calculating tank weights:
- Water 8.3 lbs per gallon
- Gasoline 5.6 lbs per gallon
- Diesel Fuel 6.8 lbs per gallon
- Propane 4.2 lbs per gallon
When contemplating the purchase of a new RV one of the first things you should look at is the CCC rating. Some RVs can get fairly heavy and are really pushing the GVWR without being loaded. If you don't have enough CCC you won't be able to haul anything so make sure that you have a CCC rating adequate for your needs to eliminate problems down the road.
Federal law prohibits any one axle from carrying more than 20,000 lbs. This is called the Federal Bridge Law. That's the reason that you see tag axles on the heavier and longer coaches. A standard rear axle with dual can only hold 20,000 lbs. The tag axle will add another 10,000 lbs to the GVWR and generally it only "costs" about 4,000 to 6,000 lbs to add the tag axle and a couple of feet of extra coach (depending upon how deluxe the construction is) so you will gain between 4,000 and 6,000 lbs by going with a tag axle, depending upon how much longer your coach grew. Front axles seem to be topping out around 14,600 lbs right now but it wasn't that long ago that 12,000 lbs was a typical front axle. That's about it because the only way to get much higher on a front axle would be to go with dual tires, which wouldn't work very well on a steer axle, or rough riding heavier duty truck tires.
Submitted by Mark Quasius - 3/29/06
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