What is the acceptable diameter range for the lower section of a kingpin?

The acceptable diameter range for the lower section of a kingpin is 1-7/8” to 2”. This specification is critical because the kingpin plays a vital role in the articulation of the trailer and ensures the stability and safety of the entire trailer system. A properly sized kingpin allows the advance and withdrawal of the trailer safely from a fifth wheel, which is essential for maneuverability and secure coupling.

In this context, other options reflect incorrect sizes as they either exceed the typical dimensions for lower kingpins or are not widely recognized as industry standards. This precision in measurement is crucial because using a kingpin outside the recommended range could lead to compatibility issues with the fifth wheel, causing safety hazards while on the road. Thus, adhering to the specified measurements ensures the structural integrity and proper functioning of trailer equipment.