How should the trailer height be adjusted before coupling?

Adjusting the trailer height before coupling is crucial to ensure a secure connection between the trailer and the tractor. The correct approach is to set the trailer height slightly lower than the fifth wheel. This configuration allows the trailer to be positioned correctly onto the fifth wheel when backing the tractor in, enabling the kingpin to slide into the fifth wheel locking mechanism.

When the trailer is positioned lower than the fifth wheel, as the tractor backs up, the weight of the trailer will pivot the trailer upward, allowing the kingpin to engage properly into the fifth wheel. Once the trailer is coupled, the weight will press the trailer down onto the fifth wheel, creating a solid connection.

If the trailer were higher than or level with the fifth wheel, it would make it difficult to achieve a secure connection, potentially leading to misalignment and unsafe conditions during transport. Ensuring the proper height not only aids in correct coupling but also is essential for safety on the road.