Truck Nuts. Kent "Mr.Truck" Sundling

that’s why we’re “truck nuts.” We will help you with the “truth about trucks and trailers.”

      GCWR is a truck plus loaded trailer for a maximum rating. Truck manufacturers subtrac the truck’s curb weight from GCWR for an approximation of the truck’s maximum towing capacity. The real world formula is GCWR minus what your truck really weighs with the cargo it carries, passengers, and fuel for the real allowable maximum trailer weight. The weight will work for static loads in your trailer like hay or cars or gold. For animals like horses, my rule of thumb is 15 percent less trailer load. Big animals move around swatting flies with their tails, and have a higher center of gravity.

      Now that you know your maximum trailer weight, next is your payload. Payload isn’t just what goes in your truck bed, it’s also the trailer tongue weight, passengers, the 45 cal. under your seat, and tools in your box. Payload is important, and many trucks have too low of a max payload capacity to use its maximum trailer weight. Payload is important for towing trailers. Bumpers that pull trailers over 5,000 pounds at 10 percent tongue weight need Weight Distributing Hitches with built-in sway control. Newer duallys have more payload capability, which allows heavier trailers. Too many trucks don’t have enough payload capacity. The simple formula for payload is GVWR minus CW (curb weight) equals PL (payload).

      It is important to remember that after you figure what your trailer weighs loaded, generally a bumper pull tongue weight will be 10 to 15 percent on a balanced trailer and 15 to 25 percent for a gooseneck/mini 5th-wheel tongue weight. The catch is the tongue weight comes off your truck’s payload. Now with that number, do you have enough left for passengers? Sometimes not, which seems to be a trend with truck manufacturers. New trucks will have a high trailer weight capacity, but with a tongue weight that won’t let you ever reach that big trailer number. Unless, of course, you don’t have passengers and the driver only weighs 100 pounds. My left leg weighs 100 pounds.

      Weigh-Safe tongue weight scale

      Tongue weight: do you know yours? Did you weigh your truck and trailer? After you know what your loaded trailer weighs, now what’s the tongue weight? Weigh-Safe has a billet aluminum adjustable receiver hitch, but it has a built-in scale. Now you can know your tongue weight each time you tow.

      Enter the SAE J2807 (Society of Automotive Engineers) to save us. The SAE J2807 standard started in 2008 to help judge real truck capacity instead of marketing with all the extreme ads. But like Congress, a good idea doesn’t make it without being diluted to a useless guideline. It is not a totally useless SAE standard, but watered down in favor of truck manufacturers who make up the committee that votes on it. Some trailer manufacturers and hitch companies are also on the committee, but the most influence is from the truck side; like the fox put in charge of the hen house. I agreed with most of the initial J2807 guidelines, with 20 percent tongue weight for gooseneck/fifth wheel trailers. Then it was changed to 15 percent tongue weight. But it’s still a guideline and not a law. So 15 percent on a gooseneck can be 20 percent. If road conditions are bad, the extra tongue weight on a gooseneck is safer. I followed a dually with a light tongue and watched him roll off the road on snow. Semi-trucks have 40 percent or more tongue weight and do better on ice. Traction comes from weight and good tires. We try to follow J2807 guidelines reviewing trucks, but if the weather is bad, I recommend 20 percent or more for control.

      The rest of SAE J2807 is helpful when comparing trucks’ towing capacity and a whole lot better than watching new truck ads on TV.

      Summary of the Rules:

      1) Cooling capability towing a trailer on a twelve-mile highway upgrade near Davis Dam in Arizona with temperature near 100 degrees.

      2) Launch and acceleration performance on a level road and a 12 percent upgrade with a trailer.

      3) Combined handling performance—understeer, oversteer and trailer sway.