2009 Toyota Tundra CrewMax Owners Manual - Page 290

2-5. Driving information Gross trailer weight Tongue load 2. Fifth wheel Towing The king pin weight is 15 to 25% of the Gross Trailer weight. (King pin weight/Gross trailer weight x 100 = 15 to 25%) CrewMax models: Current fifth wheel trailer designs are not compatible with short bed. The gross trailer weight and tongue load can be measured with platform scales found at a highway weighing station, building supply company, trucking company, junk yard, etc. Gross trailer weight King pin weight 260