The ratings that limit what you can tow
A truck’s advertised towing capacity is only one of several limits, and it is often not the first one you hit. Check every rating on the door-jamb sticker and in the owner’s manual:
- GVWR (gross vehicle weight rating): the maximum weight of the loaded tow vehicle, including passengers, cargo and the trailer’s tongue weight.
- Payload capacity = GVWR − curb weight. Passengers, cargo, accessories and tongue weight all count against it.
- GCWR (gross combined weight rating): the maximum weight of the loaded truck plus the loaded trailer.
- Towing capacity: the maximum trailer weight, usually calculated for a base truck with only a driver aboard.
- Hitch rating: the receiver and ball mount have their own maximum trailer and tongue weights.
Example
A pickup with a 7,000 lb GVWR and a 5,200 lb curb weight carries 600 lb of passengers and gear and tows a 6,500 lb travel trailer with 12% tongue weight:
- payload capacity: 7,000 − 5,200 = 1,800 lb;
- tongue weight: 780 lb; payload used: 600 + 780 = 1,380 lb; 420 lb left;
- gross combined weight: 5,200 + 600 + 6,500 = 12,300 lb, 2,700 lb under the 15,000 lb GCWR;
- the trailer uses 72% of the 9,000 lb towing capacity.
Everything is within limits. Adding a family of four and a bed full of firewood would quickly use up the remaining payload, even though the “towing capacity” still looks generous.
Tongue weight
For a conventional bumper-pull trailer, tongue weight should be 10 to 15% of the loaded trailer weight. Too little causes dangerous sway; too much overloads the rear axle and lightens the steering. Fifth-wheel and gooseneck trailers put 15 to 25% on the pin. Measure it with a tongue weight scale or at a truck scale, and load heavy gear ahead of the trailer axle.
The 80% rule of thumb
Many RV and towing experts advise keeping the trailer at or below 80% of the rated towing capacity. This leaves a margin for headwinds, grades, heat and the extra weight of water, propane and gear that trailers almost always carry beyond their dry weight.
Practical tips
- Use the trailer’s loaded weight or its GVWR, not the brochure’s dry weight.
- Trailers above 3,000 lb generally need their own brakes, by state law, and a brake controller in the truck. Thresholds vary by state.
- A weight-distribution hitch shifts some tongue weight back to the front axle and the trailer axles. It does not increase any rating.
- Weigh the full rig at a CAT scale before a long trip.