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| A Weighty Issue: Shipping Weight and Curb Weight |
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| Written by Aaron Severson |
| Monday, 14 December 2009 15:14 |
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A car's weight has a dramatic effect on its performance, ride, handling, and fuel economy. Figuring out how much a car weighs should be simple, but the weights listed in brochures, road tests, and other sources can be contradictory and confusing. A vehicle's specifications may list shipping weight, manufacturer's curb weight, and gross vehicle weight ratings, all of which are quite different. Dry WeightDry weight is a vehicle's unladen weight with a completely empty fuel tank and no engine oil, coolant, or other fluids. As you can probably guess, dry weight is consequently much less than the car's actual, on-the-road weight. A gallon of water weighs about 8.4 lb (3.8 kg), a gallon of gasoline about 6.3 lb (2.9 kg), so just adding fluids and filling the gas tank can add 150 lb (68 kg) or more to a car's dry weight.
Since passenger cars are generally (though not always) shipped with oil, coolant, and other vital fluids, dry weight is not often quoted for complete automobiles, although the term is sometimes used, albeit not always correctly, as a synonym for shipping weight. However, the quoted weights of automotive engines are almost always dry weights (and may or may not include accessories or the weight of the flywheel or flex plate). Shipping WeightUnless you pick up your new car directly from the factory, the manufacturer has to ship it to dealers by sea, rail, or truck. Because freight charges are usually based on weight, automakers frequently publish a standardized shipping weight for each model they sell. If a model is available with a choice of "standard" engines -- e.g., a mid-1960s Chevrolet with either a six or a V8 -- the manufacturer will sometimes list separate figures for each engine, or quote the additional weight added by the larger engine and its associated equipment.
Shipping weight usually reflects a "stripped" model, with a standard engine and no optional equipment. It typically includes engine and transmission oil, engine coolant (if the engine is water-cooled), and at least a modicum of fuel, enough to start the engine and drive the car off the truck or transport pallet. In some eras, however, filling the radiator and fuel tank were left to the dealer. As a result, it's not easy to be sure whether quoted shipping weight included those fluids without detailed knowledge of a particular automaker's standard procedures in that period. Like dry weight, shipping weight is usually substantially less than the car's actual, ready-to-drive weight. Aside from the weight of fuel, optional equipment or engines can add a great deal to the car's total mass. For example, as 1965 Ford Mustang with the optional 289 cu. in. (4.7 L) V8, automatic transmission, power steering, radio, and power brakes weighed at least 400 lb (181 kg) more than a stripped six-cylinder model. Adding to the disparity, a lot of equipment we now take for granted, such as heaters, turn signals, and even spare tires were at least nominally optional in earlier eras. It's unlikely that many cars were built without those features, except perhaps by special order for fleet buyers, but since they were not technically standard equipment, their weight was not reflected in the published shipping weights. Shipping weight is best understood as a particular model's practical minimum weight in stock form. For that reason, some racing organizations have used factory shipping weights to determine eligibility for different racing classes. (Depending on the rules of the specific class, a minimum weight figure may also be imposed to limit competitors' ability to further lighten the car by removing trim and standard equipment or substituting lightweight components.) Curb WeightA vehicle's curb weight (or kerb weight, for our British readers) is its weight in ready-to-drive condition, with fuel in the tank and all necessary fluids, but without a driver, passengers, or cargo. In the United States, curb weight is usually measured with a full tank of fuel. In other countries, manufacturers or testers may list curb weight with only a small amount of fuel, which can result in substantial discrepancies between sources.
The manufacturer's curb weight is the curb weight listed in the automaker's official specifications. As with shipping weights, these figures generally do not include optional engines or equipment. Some manufacturers specify an average figure, or list separate curb weights for each model and powertrain combination. Most simply list the weight of a stripped model, although automakers occasionally publish lists specifying the additional weight of major options, such as automatic transmission or air conditioning. Some independent auto testers weigh each of the vehicles they test, and list the vehicle's actual curb weight in the test results. These figures are typically higher than the manufacturer's figures, because they include whatever optional equipment the car actually possesses, rather than the standardized figure. Some magazines and testers also list the actual test weight of their subjects, which is the curb weight plus the weight of the driver and any test equipment. In the 1950s and 1960s, in particular, test weights were often substantially higher than curb weights, reflecting the bulk of period test equipment and, in some cases, the necessity of carrying a passenger to operate it. Gross Weight and Gross Vehicle Weight Rating (GVWR)A car's gross weight is its curb weight plus the weight of its driver, passengers, and cargo. A car's gross vehicle weight rating (abbreviated GVWR, but often confusingly listed as just gross weight) is the manufacturer's recommended maximum loaded weight. The vehicle's maximum load is the GVWR minus the curb weight. For example, a Honda Odyssey EX minivan has a manufacturer curb weight of 4,475 lb (2,030 kg) and a gross vehicle weight rating of 5,952 lb (2,700 kg); its maximum load is 1,477 lb (670 kg). Naturally, a vehicle's actual gross weight changes depending on how many passengers and how much cargo it's carrying, but its gross weight rating does not.
Gross weight ratings usually assume the standard suspension and standard tires, inflated to the recommended pressure. Manufacturers occasionally specify different gross weight ratings for different combinations of suspension and tires, although that is more common for trucks than for passenger cars. In many nations, including the U.S., gross weight rating determines what roads a vehicle is permitted to use, what type of driver's license and insurance are necessary to operate it, and the emissions and fuel economy standards it must meet. APPLES TO ORANGESAt Ate Up With Motor, one of our goals is to put each of the cars we discuss in context, both with other cars of its time and with modern vehicles. Unless otherwise noted, when we refer to a car's weight, we mean its actual curb weight, not its shipping weight or gross weight rating.
The weights we quote are often approximate, reflecting the fact that different combinations of engines and options can produce huge variations. If you compare those figures with the specifications of other cars (or figures listed in different sources), be sure to note whether the numbers to which you're comparing them are referring to curb weight or shipping weight -- as you can see, it can make an enormous difference! # # #
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Great info. So cars in the 60s (Supercars as you call them on the site) not only had misleading horsepower figures but misleading weight as well? Testing equipment (even at racetracks and etc) would also have been much less accurate than modern equipment.
Suddenly it doesn't seem as weird to read that modern economy cars are just as fast or faster than the Supercars of old. I will have to remember all this when reading figures on my old favorites.