This SAE Standard applies to upper coupler kingpins for commercial trailers and semitrailers in the unladen condition. See Figure 1. A 90 degree ± 1 degree angle extends (in all directions) from the centerline of the kingpin to the upper coupler plate surface within a 48.26 cm (19 in) radius. The upper coupler plate surface should not bow downward (convex) more than 0.635 cm (1/4 in) within a 48.26 cm (19 in) radius or more than 0.3175 cm (1/8 in) at a radius of 25.4 cm (10 in) from the kingpin. The upper coupler plate surface should not bow upward (concave) more than 0.15875 cm (1/16 in) within a 48.26 cm (19 in) radius. (See Figure 2.) NOTE--For recommended performance, see SAE J133.
The Truck and Bus Coupling & Interchangeability Committee which owned this report has become inactivated and the technical expertise for the subject report within the Truck and Bus Council is not available at this time. This standard has been transferred to the Total Vehicle Steering Committee to stabilize the standard.