Vehicle towing capacity

Some numbers associated with cars and trucks really aren't a mystery. In fact, they're pretty straightforward. For example, most everyone knows what fuel economy numbers are. Even horsepower and torque numbers are familiar to many these days. A vehicle's zero to sixty times are often mentioned when you're discussing a sports car, and if you're talking about a sedan, you might even be familiar with numbers that describe how much interior space that model has to offer -- numbers that describe the interior volume or the front and rear seat leg room. These numbers -- along with many, many others -- are important to understand when you're buying a car or truck. They clearly describe to you what you can expect to get for your money.

Even though all of these costs, statistics, weights and measures are published, or somehow available to consumers, there are still a few numbers that cause some confusion among new car and truck buyers. Truthfully, most people don't even know what some of these numbers really mean, or the consequences of ignoring them. One example is a vehicle's gross combination weight rating, or GCWR.

If you're ever planning to tow a trailer with your vehicle -- whether it's a car, truck or SUV -- you should be aware of your gross combination weight rating, so you should probably start by learning the definition of a GCWR. A vehicle's GCWR is a specific weight determined by the manufacturer to be the maximum weight of a loaded tow vehicle and its attached loaded trailer. The total weight of the tow vehicle and trailer should never exceed the manufacturer's listed GCWR [source: Ford Motor Company].

Similar to a vehicle's gross vehicle weight rating, or GVWR, the gross combination weight rating is a specific maximum weight limit determined by the manufacturer. The major difference is that the GCWR takes into account two individual (yet attached) vehicles -- the tow vehicle and the trailer. However, the gross combination weight rating definition doesn't really state how the weight rating is calculated. According to Ford Motor Company, the GCWR is calculated by adding the following weights together: The vehicle's listed curb weight, allowable payload, driver and passenger weight and trailer weight [source: Ford Motor Company].

It's important to remember that the GCWR is not an actual measurement of the weight of a tow vehicle and a trailer, but rather the combined maximum weight limit that the manufacturer has set for the two vehicles once attached.

The primary reason for setting a GCWR for any vehicle is safety. Overloading a tow vehicle or a trailer is dangerous enough. Overload both and you've really got a problem. Not only is a heavy load difficult to control on the road, but several other components could also be at risk. For example, the braking systems may overheat and fail, reducing or even eliminating the possibility of safely slowing or stopping your vehicle. The tires may not be able to handle the extra load, potentially causing a blow out situation. The engine and transmission in the tow vehicle may overheat due to the added strain, causing a mechanical failure. Components within the tow vehicle or trailer's suspension system could bend or even break, causing you to lose control on the road. The truth is that a variety of problems could result from overloading. Again, you should never surpass your vehicle's GCWR.

If you're going to tow a trailer, it's a smart move to play it safe by learning your vehicle's GCWR. Where can you find this information? Typically, it can be found on a label inside the vehicle's door frame, near the area where the driver's door latches. Another option is to search for the information on the Internet. Most manufacturers will publish this and other important vehicle information online.

How Cargo Carrying Capacity (CCC) Works

Most people can easily determine when they're adding a little too much cargo weight to the family vehicle. For example, let's just say you were at the local home improvement warehouse store shopping for new ceramic tile. If you were to load box after box of ceramic tile to the cargo area of your hatchback subcompact car, it wouldn't take very long for you to realize that you were overloading the rear suspension. In fact, after loading just a few of the heavy boxes of tile into your car, you'd likely see that your rear bumper is noticeably closer to the pavement and your front bumper is moving upward just as quickly. In this case, it's very easy to establish that your small car is just not designed to carry that much weight.

Even if you had a pickup truck or SUV, there's a good chance that you might still see similar results. Of course, it would take a lot more weight (in this case, several more boxes of tile) to make the back end of a pickup truck or SUV sink like that because they're designed to carry much more cargo weight.

Now imagine that you were loading those boxes of tile into a massive recreational vehicle (RV). Unless you purchased an abnormally large amount of tile, you really wouldn't even know that the boxes of tile were there unless you actually looked inside. The reason is because some of the really big RVs are designed to carry a lot of cargo weight.

So how would you ever be able to determine if you were overloading an RV? After all, recreational vehicles carry things like furniture, appliances, televisions and people -- often lots of people. How much is too much? The short answer is that you would need to know the RV's cargo carrying capacity, or CCC. The long answer involves a little bit of simple math and a few definitions. Here's how to calculate an RV's cargo carrying capacity:

•Start with the vehicle's gross vehicle weight rating (GVWR)

•20,000 pounds (GVWR)

•Subtract the vehicle's unloaded vehicle weight (UVW)

•The UVW is a manufacturer provided weight measurement of the vehicle that includes a full tank (or tanks) of fuel, coolant and oil

•14,500 pounds (UVW)

•Subtract the weight of the sleeping capacity weight rating (SCWR)

•The SCWR is another manufacturer provided weight measurement (a maximum weight) determined by multiplying 154 pounds times the number of sleeping positions

•924 pounds (SCWR) (6 sleeping positions x 154 pounds)

•Subtract the weight of the propane fuel (LP gas)

•Propane weighs 4.2 pounds per gallon

•50.4 pounds (LP gas) (12 gallons x 4.2 pounds)

•Subtract the weight of the fresh water on board

•Water weighs 8.3 pounds per gallon

•207.5 pounds (fresh water) (25 gallons x 8.3 pounds)

•The result is the cargo carrying capacity (CCC) of the vehicle

•4,318.1 pounds (CCC) (cargo carrying capacity)

It's important to understand that the cargo carrying capacity definition, as outlined for you here, is a weight limit, or maximum weight, as determined by the vehicle's manufacturer. For safety's sake, the RV CCC should never be exceeded.

If you're curious about your own vehicle's cargo carrying capacity, the manufacturer should be able to provide you with this data. Another option is to search for the information on the Internet. Most manufacturers will publish this and other important vehicle information online.