Perhaps no other vehicle segment is as obsessed about specifications and capabilities as full-size trucks. Midsize sedan models brag about best-in-class fuel economy, interior room, and trunk space, but if you were to ask your typical Honda Accord owner what the final drive ratio was on his transmission, chances are, you'd just get a blank stare and a shrug.

Full-size truck owners, on the other hand, tend to be veritable statistical geeks on their rides, being able to quote everything from axle ratio to payload, lifetime mpg, and recommended tire pressures. And there are dozens of factors that determine a trucks' maximum capacity, and a particular trim and model's capacity may increase in one area, while decreasing in another. To help shed some light on the sometimes confusing terminology and acronyms used in the truck world, we've broke down some of the key terms:

Curb Weight
The vehicle's weight "at the curb" (i.e., without the driver). But curb weight does include fuel and fluids. This is the measurement used for most passenger cars, trucks, and SUVs. Many off-road powersports vehicles such as quads, motorcycles, and side-by-sides are rated in "dry" weight, meaning without fuel, lubricants, and coolant.

Gross Vehicle Weight Rating (GVWR)
This number is the one that separates the men from the boys, or more accurately, the half-tons from the HDs. But by Department of Transportation standards, even the so-called "HD" trucks are considered light-duty. Half-ton, 1500, or 150-series trucks (depending on the brand) are rated up to 8500-pounds GVWR, which is the combined maximum allowable weight of the vehicle, fuel, fluids, passengers, and payload. Let's say you weigh about 200 pounds, and you have a 30-gallon fuel tank full of gasoline. You have another passenger who weighs about the same amount.

With the approximate weight of a gallon of gasoline at 6.1 pounds, that's 183 pounds of fuel, and 400 pounds worth of passengers. Motor oil weighs approximately 1.8 lb per quart, so multiplied by eight quarts, that's 14.4 pounds of oil, a gallon of mixed coolant weighs approximately 9 pounds. Most trucks have a cooling system capacity of about 16 quarts, or 4 gallons, so that's 36 pounds of coolant. Adding all these weights together gives you 633.4 pounds, an amount you should effectively subtract from the truck's rated GVWR -- in addition to subtracting the curb weight -- to give you your effective payload capacity, although there are other factors that determine payload as well.

Payload
Put simply, payload is the carrying capacity of the truck itself, separate from its towing capacity. Pertinent to today's market where crew cab trucks represent a substantial slice, if not the majority of full-size truck sales, payload also includes the weight of any cargo and passengers inside the cab. So that means hauling around two or three of your 250- pounds beer-drinking, rib-chompin', football-watchin' buddies will decrease your maximum effective bed payload capacity by a proportionate amount. A quick formula for determining payload capacity is taking the vehicle's Gross Vehicle Weight Rating and subtracting the Curb Weight.

Gross Combined Weight Rating (GCWR)
The Gross Combined Weight Rating is the GVWR plus the towing capacity. So that's you, your buddies, your tank of gas, oil and coolant, the cooler full of beer and food in the back, plus the weight of your ski boat (or toy hauler, or camper trailer, etc.).

Gross Axle Weight Rating (GAWR)
There are actually two GAWRs for your truck. Front and rear. Front and rear ratings are usually designated by FR or RR to signify front or rear capacities. The GAWR includes the weight of the components, as measured at the tires. Typically, the rear axle rating is slightly higher, in accommodation of payload. Rear GAWR may be close to, but is not the same as payload capacity.

Gross Trailer Weight (GTW)
Weight of a trailer, and all items on board, including fuel, liquids, belongings, etc.

Tongue Weight
Tongue weight is the downward force the trailer applies to the hitch. Tongue weight will typically fall between 9 and 15 percent of the Gross Trailer Weight. A proper tongue weight is important for safety reasons. Too light, and the trailer could be in danger of coming off the hitch. Too heavy, and the towing vehicle's steering could be adversely affected.

Fifth-Wheel Capacity
Fifth-wheel towing capacity generally applies to the larger ¾ and 1-ton trucks. It's the rated towing capacity for a so-called "gooseneck hitch" trailer, which locates the trailer hitch in the middle of the bed, usually near or on top of the rear axle centerline. Especially when towing heavier loads, this method of weight distribution is much safer. The 2013 Ram 3500's headline-grabbing 30,000-pound capacity is measured with fifth-wheel towing. A "fifth wheel" hitch consists of a rig with a horseshoe-type connector similar to those used on Class 8 trucks. A gooseneck hitch can be a ball hitch attached directly to the truck bed, or in a smaller, less elaborate bolt-on rig than a fifth-wheel hitch.

Conclusion
When shopping for a new (or used) truck, it's important to do your homework on its rated capacities, and take into consideration what you'll primarily be using it for. If you don't know the load of your typical trailer or payload, find a truck scale in your area, and pull your truck on it unloaded and with a typical load, either payload or trailer. To be on the safe side, it's always a good idea to buy a truck with a rated load higher than what you'll usually be towing or hauling. This will ensure the truck's chassis, drivetrain, and suspension will not be asked to do more than it was designed for, and likely save you repair and maintenance headaches down the road.