Glossary for Towing and Vehicle Weight Terms
Gross Combination Weight Rating (GCWR)—The GCWR is the maximum allowable weight of the tow vehicle and the trailer combined. The GCWR may be found in the Owner's Manual or in the tow vehicle brochure for the model year you own, usually provided by the dealership. Some late-model vehicles may have a “Trailering Information” label providing the GCWR. The GCWR assumes that the tow vehicle and trailer have functioning brakes, with exceptions, in some cases, for very light trailers (typically less than 1,500 pounds). The GCWR information for your vehicle may be found at FifthWheelStreet.com under the Tow Rating menu tab. Additionally, you may learn more about GCWR by reading our article, A Lesson on Gross Combination Weight Rating.
Important Note About GCWR—When any calculation is based solely on the GCWR, regardless of any calculator or what a salesperson may calculate, one still needs to be careful not to overload the rear axle. In most situations like this, the towing capacity is limited by the published maximum towing capacity (TWR), which supersedes any calculation results. Some manufacturers derate towing capacity (usually for conventional towing). Example: The GAWR may be exceeded when calculating this vehicle information: GCWR: 22,800, GVWR: 10,000, GVW: 6026, rear GAWR: 6,000. The published max tow of 16,300 (TWR) supersedes the GCWR calculation of 16,774. (i.e., GCWR-GVW=Tow Capacity)
Gross Vehicle Weight Rating (GVWR)—The GVWR is the maximum allowable weight of the fully-loaded vehicle, including liquids, passengers, cargo, and kingpin or tongue weight of any towed trailer. The GVWR is printed on the certification label, usually located near the driver's side door. This information can be found on the Trailering Information label on some late-model vehicles.
Vehicle Certification Label Indicating GVWR
Trailering Information Label Indicating GVWR
The GVWR, as required by National Highway Traffic Safety Administration (NHTSA), primarily considers the weakest link in the load-bearing components such as the frame, axles, springs, brakes, rims, and tires. Based on the lowest component rating within the load-bearing components, manufacturers assign the GVWR. NHTSA's safety requirement for GVWR is that it is expected to stop within a required distance when it is fully loaded to the max GVWR. This appears to be a primary safety concern of NHTSA when tow vehicles are overloaded by too much pin or tongue weight coming from the trailer. Some owner's manuals may state: "The towing vehicle's brake system is rated for operation at the GVWR—NOT GCWR. Separate functional brake systems should be used for safe control of towed vehicles and for trailers weighing more than 1,500 lbs. when loaded." Exceeding the GVWR can result in premature mechanical failure and failure to stop within a safe distance resulting in severe injury or death.
Additional resource: 49 CFR 571 - FEDERAL MOTOR VEHICLE SAFETY STANDARDS (Title 49 Transportation, Part 571)
Gross Vehicle Weight (GVW)—The GVW is the vehicle's combined weight with all expected passengers, including cargo, towing hitch installed, and fluid tanks full. It is best to weigh your vehicle when fully loaded. Appropriate fluid tanks should be full. All expected passengers should be aboard just as if you were ready to tow to the trip destination, including desired cargo. When a new vehicle purchase is involved, it may be necessary to use the manufacturer's published vehicle curb weight.
Curb Weight (Kerb Mass)—The curb weight of your vehicle is the weight of the automobile with all of the standard equipment and necessary operating consumables (e.g., motor oil and coolant) and a full tank of fuel, but without any passengers, cargo, or any other separately loaded items in it. Thus, the curb weight is when the vehicle weighs is resting at the curb and not in use. This is generally the standard weight that the manufacturer assigns to the car. The manufacturer-assigned curb weight of a vehicle may not be the same at the time of purchase due to dealer-installed components or options. The curb weight information for your vehicle may be found in the Owner's Manual, the Trailering Information label, or at FifthWheelStreet.com under the Tow Rating menu tab.
A Note About Curb Weight—When the only option is to use the manufacturer's published curb weight, it is important to provide, as accurately as possible, the additional weight of the expected cargo and passengers, and, if desired, select the fifth wheel hitch option on the app when a hitch is not installed or the fifth wheel hitch weight is unknown.
Trailer Weight Rating (TWR)—TWR is the rated value for the maximum allowable weight of a loaded trailer for a specific tow-vehicle model and hitch type, as determined by the tow-vehicle manufacturer. A specific tow-vehicle may have multiple TWRs for weight carrying hitch, weight distributing hitch, fifth wheel hitch and/or gooseneck hitch. A tow-vehicle may also have a TWR for an unbraked trailer. (SAE J2807 definition)
TWR is also known as Maximum Loaded Trailer Weight or Max Trailer Weight Rating or Max Towing or Max Towing Capacity. Some late-model vehicles may have a “Trailering Information” label providing the TWR.
Some manufacturers will derate the towing capacity below the available payload (GVWR) and GCWR calculations. Additionally, the TWR may be a derated rating to prevent the rear gross axle weight rating (Rr. GAWR) from being exceeded on select vehicles.
The published TWR will always supersede higher towing capacity results from GCWR and GVWR mathematical formulas.
Tongue Weight (TW)/Pin Weight (PW)—TW (for conventional trailers) and PW (for fifth wheel trailers) is the vertical load weight applied to a hitch. Generally, TW should range between 10% to 15% of the conventional trailer's GVW, and the PW of fifth wheel trailers should range between 15% to 25% of the trailer's GVW. Note: SAE recommends the TW to be 10% and the PW to be 15% for optimum towing performance. Some late-model vehicles may have a “Trailering Information” label providing the maximum TW/PW allowed.
Tow-vehicle Trailering Weight (TVTW)—TVTW is base vehicle curb weight plus one 150 pound driver and one 150 pound front seat passenger, plus100 pound of optional equipment split evenly between front and rear axles, plus the tow-vehicle manufacturer’s available trailering package and/or any required trailering content and representative aftermarket trailering equipment. (SAE J2807 definition)
Tow Ready Vehicle/Truck—The fully-loaded vehicle or truck with the driver and all passengers on board, all desired cargo onboard, necessary trailering equipment installed, and necessary vehicle fluid tanks or reservoirs filled to standard or full capacity.
SAE J2807—This document defines procedures and requirements to determine Gross Combination Weight Rating (GCWR) and calculate corresponding Trailer Weight Rating (TWR) for any tow-vehicle. These procedures will establish consistent rating requirements and processes so end-users (customers) can reasonably compare similar class models in terms of trailering ability. More information on the SAE J2807 standard may be read here: SAE J2807 Tow Tests
Realistic Vehicle Towing Capacity (RVTC)—This is a term I developed in association with using RV Tow Check. RVTC is obtained after the tow vehicle is configured tow-ready. Then calculation formulas for GCWR and GVWR are completed and compared with the published TWR to learn the realistic vehicle towing capacity.
RVTC is also the initials for RV Tow Check.
Note: We have interpreted glossary terms from the UK and Australia the best we know how. If you are from one of these countries and find a mistake or can provide an improved interpretation or web link, please contact us.