Which component connects the trailer to the tractor and allows it to pivot?

• A. Kingpin on the semi-trailer.
• B. Brake chamber.
• C. Air line coupling.
• D. Landing gear.

Answer: (A)

The connection that links the trailer to the tractor and lets it pivot is the kingpin on the front of the trailer. It fits into the fifth wheel on the tractor and is locked by the jaws, allowing the trailer to rotate as the tractor steers while staying attached. The kingpin carries the vertical load and provides the articulated connection that makes towing possible.

The brake chamber, air line coupling, and landing gear have different roles: brake chamber actuates the braking system with air pressure, air line coupling connects the tractor and trailer’s air lines, and landing gear supports the trailer when it’s detached from the tractor.