184.108.40.206 Fifth wheel type. Truck tractors shall have a 910 mm (36-inch) diameter fifth
wheel. The fifth wheel shall have forks and semiautomatic lock for a 50 mm (2 inch) SAE J700
kingpin or, when specified (see 6.2), a 89 mm (3-1/2 inch) SAE J848 heavy duty kingpin.
Unless otherwise specified (see 6.2), model 4x2, 6x4 and 8x6 shall have a fore and aft rocking
fifth wheel and model 4x4, 6x6 and 8x6 shall have a full oscillating fifth wheel. Side oscillation
shall have a lockout.
220.127.116.11 Fifth wheel features. All fifth wheels shall have an uncoupling mechanism on
the driver's aide of the vehicle. The uncoupling mechanism shall have a secondary lock,
preventing operation of the primary lock until the secondary lock is manually released. The
vertical load ratings and the drawbar pull ratings of the fifth wheel shall be not less than the loads
imposed with the truck tractor loaded to specified GVW and GCW.
18.104.22.168 Fifth wheel location. In addition to the following, see 22.214.171.124 for weight
distribution requirements on fifth wheel location.
126.96.36.199.1 Swing radius (SR). The clearance SR shall be not less than 1620 mm
(64 inches). The clearance SR shall be measured from the centerline of the kingpin to the cab, or
to the vertical spare tire assembly when furnished, or to the pogo-stick type hose tender. When
additional equipment to be mounted behind the cab is specified, the SR clearance shall be
measured to the rearmost point of a pogo stick that shall be mounted behind the additional
188.8.131.52.2 Landing wheel clearance (LWC). The LWC dimension shall be not more than
1620 mm (64 inches) on model 4x2 and 4x4 and 2030 mm (80 inches) on model 6x4, 6x6, 8x4
and 8x6. The LWC dimension shall be measured from the centerline of the kingpin to the rear
tires, the chassis frame rails, the tail roller and the pintle.
184.108.40.206.3 Class 32 4x2. In addition to the foregoing, the centerline of the fifth wheel for
class 32 4x2 tractors shall be not less than 360 mm (14 inches) forward of the centerline of the
220.127.116.11 Fifth wheel mounting. Fifth wheel mounting shall conform to
18.104.22.168 Fifth wheel height. The unladen level height of the fifth wheel shall conform to