During a coupling device inspection, which part must rotate freely?

The fifth wheel plays a crucial role in the coupling device of a trailer, especially in commercial vehicles. Its primary function is to provide a pivot point that allows the trailer to articulate while being towed. For the vehicle to operate safely and effectively, it is essential that the fifth wheel rotates freely. This freedom of movement helps absorb shocks during travel and allows for proper turning and maneuvering without causing excessive stress or damage to the hitching mechanism or the trailer itself.

The other components listed do have their own specific functions and requirements during an inspection. Safety chains are designed to provide an additional safety measure in case the primary coupling fails but do not need to rotate. U-bolts secure components in place and typically do not involve rotational movement. Leaf springs provide support and absorb shock but also have fixed positions in the vehicle assembly. Thus, the emphasis on the fifth wheel's ability to rotate freely during inspections is imperative for the safe operation of vehicles equipped with trailers.