TOYOTA 2011 Tundra - Manual (Page 300)

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2-5. Driving information
2. Fifth wheel Towing or Gooseneck Towing
The gross trailer weight should be distributed so that the kingpin
weight is 19% to 21%. (Kingpin weight/Gross trailer weight x 100
= 15% to 21%)
Gross trailer weight
Kingpin weight
The gross trailer weight and kingpin weight can be measured
with platform scales found at a highway weighing station, build-
ing supply company, trucking company, junk yard, etc.
CrewMax models: Current fifth wheel trailer designs are not
compatible with short bed.