The gross vehicle weight rating (GVWR) measures the maximum permissible weight of a vehicle. This comprises both the mass of the vehicle or trailer itself and the maximum load weight that can safely be transported on the road. The GVWR is also known as Maximum Authorised Mass (MAM). The Gross Vehicle Weight (GVW) reflects the mass of the vehicle plus passengers and load at any given time, and must not exceed the GVWR. Obviously the GVW of a vehicle will differ somewhat on most journeys depending on what loads the driver is carrying, the weight of any passengers, fuel, attached trailers, and so forth. GVW must not exceed the GVWR for various reasons, outlined below.
A vehicle’s overall gross weight rating (GVWR, or maximum safe weight) is defined in manufacturer’s specification documents; the calculation includes various factors such as the curb weight, maximum cargo weight, estimated passenger weight and any fitted equipment that might increase the GVW. The GVWR is fixed for each specific vehicle and doesn’t ever change, regardless of any modifications you or a garage may make.
The GVWR for new and used vehicles can normally be found in various places which will include the owner’s manual. Goods wagons or vans will usually also show the value on a plate fitted to the vehicle or on a sticker fixed in a prominent place, such as the inside of a door or glovebox. For tractors and larger vehicles, it’s not uncommon to find another value known as the gross combination weight (GCW) listed on the plate or vehicle manual; this represents the total combined weight of the vehicle, an attached trailer and its load.
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Drivers should be aware of the GVWR when transporting heavy loads, especially with a trailer. In addition to possibly causing damage to a vehicle if the GVW exceeds the manufacturer’s stated figure, failure to comply with this limit may also invalidate any claims made under an insurance policy. Exceeding the GVWR is likely to reduce performance under braking in any conditions and is a huge safety risk. The GVWR figures are calculated with safety and performance in mind, and are an extremely important consideration in the motor trade.
While the GVWR is rarely a consideration for most people when looking around the forecourt or testing a car on trade plates, it’s worth researching the figures on a potential purchase before investing. This is especially true if you regularly transport heavy goods or unusually large loads.