Which of the following describes the required diameter for the upper section of a kingpin?

The correct answer emphasizes the specific requirements set forth for the upper section diameter of a kingpin. The diameter of 2-11/16” to 2-7/8” is aligned with industry standards for heavy-duty trailers and vehicles, ensuring compatibility and structural integrity under load conditions.

The kingpin plays a crucial role in connecting the trailer to the fifth wheel of the tractor. It must meet precise specifications for both safety and performance. By maintaining the correct diameter range, manufacturers ensure that the kingpin can properly fit into the fifth wheel, providing the necessary support and stability during operation.

This size specification also helps accommodate the forces encountered during towing, turning, and braking, thereby enhancing overall vehicle handling characteristics. Adhering to these dimensions reduces the likelihood of issues such as excessive wear, failure to connect properly, or instability while the vehicle is in motion. Understanding these standards is critical for inspectors who evaluate the safety and compliance of trailers as part of their duties.