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Motorhome Terms Glossary

Originally Published in MotorHome Magazine

The following definitions for commonly used RV terms and abbreviations can be useful for new RVers and seasoned travelers alike.

120 AC/12 DC/LP-gas
The power sources on which RV refrigerators operate; 120 AC is 120-volt alternating current (same as in houses); 12 DC is 12-volt direct current (same as in motor vehicles); LP-gas is liquefied petroleum gas (see LP-gas entry below). Some RV refrigerators can operate on two of the three sources, others on all three.

Axle ratio
Ratio between pinion and ring gears in the differential that multiply torque
provided by the engine. It describes the number of driveline revolutions
required to turn the axle one time. With a 4.10:1 axle, the driveline
turns 4.1 times for each full axle revolution. Higher numbers mean more
torque and less road speed for a given engine speed; i.e., a 4.10:1
ratio provides more torque than a 3.73:1.

British thermal unit (BTU)
A measurement of heat that is the quantity required to raise the temperature of one pound of water 1 degree F. RV air-conditioners and furnaces are BTU-rated.

A device for changing 120-volt AC into 12-volt DC electrical power.

Gross axle weight rating (gawr)
Maximum to which the axle can be loaded, according to the manufacturer; includes all weight placed on all tires on a given axle.

Gross combination weight rating (gcwr)

Maximum allowable combined weight of the tow vehicle and the trailer, according
to the vehicle manufacturer; includes the weight of both vehicles plus all fuel, water, supplies and passengers.

Gross vehicle weight rating (gvwr)
Maximum to which a vehicle can be loaded, according to the manufacturer;
includes dry weight of the vehicle plus all fuel, water, supplies and passengers.

Hitch weight

Amount of a trailer’s weight that rests on the tow vehicle; should be 10 to 15 percent with
conventional trailers, 15 to 20 percent for fifth-wheels.

Holding tanks
Tanks that hold the black (toilet) and gray (sink, shower, lavatory) water. Their capacity determines how long an RV can be used without hookups.

Campground facilities for connecting an RV to 120-volt AC “shore power”: water, sewer, cable TV and telephone service.

A device for changing 12-volt DC into 120-volt AC power.

Kilowatt (kW)
A measurement of electrical power; each kilowatt equals 1,000 watts.

A sandwich of structural frame members, wall paneling, insulation and exterior covering, adhesive-bonded under pressure and/or heat to form the RV’s walls, floor and/or roof.

Liquefied petroleum gas; propane is one formulation and butane is the other. Propane fuels RV appliances, such as the stove and refrigerator.

Net carrying capacity (NCC) or payload capacity
The amount of cargo, passenger and fluid weight that can be added to an RV without exceeding its gvwr. The NCC label in an RV may not include the weight of dealer- or factory-installed options already on the vehicle.

The RV’s underfloor surface, which is protected by a weatherproofing method or material.

Unloaded vehicle weight (uvw) or dry weight
Weight of the vehicle without manufacturer’s or dealer-installed options and before adding fuel, water or supplies.

Wet weight
Weight of a vehicle with full fuel and freshwater tanks.

Distance between center lines of the primary axles of a vehicle. If a motorhome includes a tag axle, the distance is measured from the front axle to the center point between the drive and tag axles.

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