[RustyJC]

If one wants to run the numbers instead of looking at overly optimistic "manufacturer's trailer towing ratings" that are calculated using a base vehicle with only a 150 lb driver, then one needs to know the truck's GCWR (Gross Combined Weight Rating - the maximum allowable total weight of the loaded truck and towed load) and GVWR (Gross Vehicle Weight Rating - the maximum allowable weight that can be carried by the truck, including the truck itself). In addition, one should run the truck over the scales loaded just as it will be when it hits the road with options, accessories (including 5th wheel hitch), full fuel tank(s), cargo, driver, passengers, etc. - this will be the truck's LCW (laden curb weight).

Truck's GCWR - Truck's LCW = maximum allowable total weight of loaded trailer

Truck's GVWR - Truck's LCW = maximum allowable pin/hitch weight of loaded trailer

A given SRW (single rear wheel) and DRW (dual rear wheel) truck may have the same GCWR - in this case, the lighter SRW truck may have a higher "manufacturer's trailer towing rating" which is calculated as GCWR - assumed curb weight. However, because of the 20%+ pin weight of the 5th wheel trailer that is carried by the truck, a SRW truck will almost always exceed its GVWR long before it reaches its GCWR or "manufacturer's trailer towing rating". This is the reason for the dually - its higher rear GAWR and GVWR ratings.

If one searches in the fine print where a manufacturer gives his trailer tow ratings, something similar to the following phrase will appear - "None of the truck's ratings are to be exceeded when towing." This is the "gotcha" that catches the SRW trucks on GVWR!

Rusty