The information in this SAE Information Report is the result of studies by the Automobile Manufacturers Association, American Trucking Association, and Truck Trailer Manufacturers Association, to achieve interchangeability of equipment which will comply with the legal dimensional limitations for the majority of states and yet permit increased loading space within these dimensions. This in no way supersedes other information in the SAE Handbook on this subject.

Some cases will require more care in application allowing splash shield clearance at trailer support interference points and positioning fifth wheel to allow trailer swing clearance on an 11% grade. All dimensions are given in inches.

Table 1 and Figures 1 and 2 show basic requirements for interchangeability of truck tractor and semitrailer equipment. Figure 3 shows the interchangeability of the doubles converter dolly.

The formulas for determining LWC, OAL and CFW are:

where:

= fifth wheel advance

= Rear axle tire radius

= 90 in

= 64 in (short trailers specifically intended for use with two axle tractors)

= 96 in

= 102 in

= Clearance, 4 in

where:

= Distance from intersection at back of cab and trailer swing radius to top of fifth wheel with zero trailer clearance to first obstruction

= Top face of fifth wheel to centerline of pivot, 3.50 in

= Swing radius of trailer corner