KNOW YOUR WEIGHTS AND HITCHES

Overloading of tow vehicles and trailers compromises safety and can result in vehicle failure. An understanding of the following terms will assist in proper vehicle selection and help prevent overloading.

Trailering Glossary

CURB WEIGHT

The weight of the empty vehicle as equipped, including a full tank of fuel. It does not include the driver, passengers or cargo - so it is similar to Dry Trailer Weight.

DRY TRAILER WEIGHT

The weight of the empty trailer as manufactured. This weight, usually found in the manufacturer's brochure, is not usually used as a measure for the selection of a tow vehicle.

GROSS VEHICLE WEIGHT RATING (GVWR)

The maximum allowable weight, as determined by the manufacturer, for any vehicle (or trailer) including the weight of the vehicle, fuel and other fluids, driver and passengers, cargo and equipment. Tongue Weight or Kingpin Weight (see below) is included when trailering.

GROSS AXLE WEIGHT RATING (GAWR)

The maximum allowable weight that can be carried on a vehicle's axle or individual suspension system, either front or rear. It includes the weight of the vehicle plus cargo and equipment supported by the axle and includes Tongue Weight or Kingpin Weight when trailering. These ratings are shown on the vehicle's Certification Label, usually located in the driver's door frame, and should not be exceeded, nor should the total load exceed the GVWR.

GROSS COMBINATION WEIGHT RATING (GCWR)

The maximum weight allowable, as established by the manufacturer, for the truck, the trailer, all equipment, total payload, fuel, fluids and occupants. This is the total loaded road-ready rig.

HITCHES

Once you have selected your vehicle, the next step is making sure you have the necessary equipment to help you trailer safely and confidently. The vehicle owner is responsible for obtaining the hitch ball, a hitch of the proper size, type and capacity, and other appropriate equipment required to safely tow the loaded trailer.

There are three categories of trailer hitches: weight-carrying, weight-distributing and fifth-wheel. Each is designed for specific types of trailering.

Weight-Carrying Hitch is the most basic and most common hitch for light and medium weights. A weight-carrying hitch uses a hitch ball mounted on a draw bar or a step-bumper and supports the trailer tongue weight just as though it were cargo located at the ball. The hitch ball must match the trailer coupler and meet or exceed the maximum trailer weight rating.

Weight-Distributing Hitch is used for heavy trailering. This hitch, with its equalizing bars and snap-up brackets, applies leverage between the tow vehicle and the trailer instead of "carrying" the load mostly on the rear of the vehicle. The brackets and spring bars raise the hitch point parallel to the ground, equalizing the load onto all axles. This results in a more level ride, reduced weight on the rear suspension and provides improved steering and braking control.

Fifth-Wheel Hitch, or gooseneck hitch, is used for heavy trailering with a full-size pickup, and it must be attached to the truck's frame, usually just slightly ahead of the rear axle centerline. Make sure to follow the manufacturer's installation instructions, paying careful attention through the box to the truck's payload capacity and rear axle weight ratings. These kingpin loads are generally higher than conventional trailer tongue loads and for most calculations becomes the payload in the truck box. The addition of kingpin weight must not cause the vehicle to exceed its GVWR or GAWRs.

LOADED TRAILER WEIGHT

The weight of the trailer (Dry Weight) plus all equipment, fluids and cargo. Loaded Trailer Weight can be determined by putting the fully loaded trailer on a commercial vehicle scale. If this is not practical, the trailer's Gross Vehicle Weight Rating (GVWR), as found in the trailer manufacturer's literature or brochures for the model selected on the trailer's certification plate, can be used when selecting a tow vehicle.

MAXIMUM TRAILER WEIGHT RATING

Often referred to as the Gross Trailer Weight Rating, it is the most weight that a given vehicle can safely and reliably haul, as determined by the manufacturer. This rating usually requires optional equipment such as specific axle ratio, suspension components, engine and/or transmission coolers and type of hitch. The rating assumes the tow vehicle is properly equipped with a driver allowance of 68 kg (150 lb.) and no cargo. The weight of additional options or equipment, passengers and cargo must be deducted from the trailer weight rating.

TONGUE WEIGHT/KINGPIN WEIGHT

The weight of the trailer tongue or kingpin that is carried on the hitch ball or fifth-wheel hitch, respectively. This is a critical measurement as it has an impact on vehicle handling. Too much Tongue/Kingpin Weight causes overloading of the rear axle, causing the front suspension to lift and reducing steering response. Too little Tongue/Kingpin Weight can reduce rear-wheel traction and cause excessive swaying or jackknifing. Depending on the type of hitch being used, Tongue Weight is generally 10-15% of the Loaded Trailer Weight. Kingpin Weight is usually 15-25% of the trailer weight. Some adjustment to Tongue Weight or Kingpin Weight can be made by moving the cargo in the trailer.