Originally Posted by kozzy
Me neither. The only thing I can think of is it has something to do with the pin weight being counted as payload perhaps? But that should still factor in to the GCWR..
Pin weight is ALWAYS payload.
Maximum trailer weight varies by manufacturer, engine options, suspension options, rear axle ratio options, wheel and tire options, and what ELSE you put in the truck besides a 150 pound driver (all of which counts against maximum payload). This pillar payload is based on your truck AS IT LEFT THE FACTORY. Dealer and your installed options (like a 5th wheel hitch, those cool wheels and tires you had them put on, and the step bars) are subtracted for your available payload. Anything you load to go camping gets subtracted too. (like the family, spare gas, etc).
You will find out quickly that truck payload will be the primary limiting factor determine the maximum weight of trailer you can tow, and not tow rating.
Since you are talking about a 5th wheel trailer, for safe handling the pin weight MUST fall between 15 and 25% of the total camper weight with the optimum pin load being 20%. 20% gives the best handling and even tire wear.
Heavier pin weights make the camper "tail light" while making the truck more stable it increases that jackknife risk in a hard stop. Lighter than 20% pin weights make the truck harder to steer and you need to be on the wheel all the time and the constant "sawing" back and forth results in higher front tire wear.
If the truck you are looking at has an available payload (found on newer truck door pillars) of say 2000 pounds. It means that with a 150 pound driver, a 150 pound 5th wheel hitch, a full tank of gas AND NOTHING ELSE, you can tow a maximum trailer weight of (using the minimum loaded pin weight of 15%) 1850 / 0.15 = 12,3333 pounds.
Using the optimally balance camper load of 20%, the same truck can tow a maximum weight 5th wheel camper of 1850 / 0.20 = 9,250 pounds.
Why is this lower than the brochure? It is because tow RATING is ONLY based on engine, drive train and rear end ratio of the truck design and NOT your truck.
To know what you can safely tow, take your truck full of gas and your hitch of choice (or a sand bag of the same weight), your family and whatever junk you normally have in the truck to a CAT scale (or similar) and get a REAL as camped weight of your truck. Subtract that number from your trucks maximum gross weight (off the door pillar) and divide that ACTUAL available payload by 0.20 to get the maximum camper you should be shopping for.
If that is too small a camper class, you can work down in pin load (but NEVER below the dry pin weight and NEVER below 15%) to see what characteristics of handling you are willing to accept with a heavier camper. If you do this plan on weighting your camper every trip for the first few outings to get a feel for how you need to load it.
Here are some weight tags for my 2008 2500HD GMC. It has a 5th wheel max tow rating of 15,400 pounds and a gross combined weight of 23,000 pounds for my year. Yet when I put it on a scale, at a 16.5% pin load I max out my truck's payload with a 9,000 pound camper.
As you can see from my yellow tag, my camper's EMPTY weight UVW as shipped from the factory is 7,218 pounds. Who would have thought.