Does The King Pin To First Bolt Measurement Matter When Replacing A Pin Box

Updated 07/20/2022 | Published 07/19/2022

Question:

I am interested in the Curt Flex Air Lippert 1621. 18k lb weight. I watched the video referencing the measurements. My current set up has same measurements EXCEPT the king pin to the first set of bolts. Mine is 19 inches. In the video he shows 21 inches. Is this acceptable or do all measurements have to be exact? I appreciate your response.

asked by: Vickie K

Expert Reply:

This measurement just means that the Curt Flex Air 5th Wheel Pin Box # LC328492 is slightly longer than your current pin box, which means that you'll have a slightly better turn radius with this pin box. The important thing here is whether or not the bolt pattern is the same otherwise you won't be able to bolt it to the trailer.

On your current pin box there should be a sticker that has serial and RPO numbers on which we can use to identify the bolt pattern. If yours does not have this then you'll need to take some measurements using the guide attached below to determine the bolt pattern.

expert reply by: Kevin C