Why Dont Extended Pin Boxes Allow Turning Clearance When Towing/Solutions for Avoiding Slider Hitch

Question:

I read post from this site a couple of months back regarding the measuring formula to determine if you need a slider. It was: 1 Measure from center of hitch jaw to the truck cab, 2 Measure from center of king pin back to the trailer overhang add these two measurements together, 3 measure width of trailer and divide by 2 to get half-width. Subtract the half-width measurement from truck/trailer measurement and you need at least 4inch or more to NOT need a slider. What I want to clarify, is where of the overhang should you measure to from the king pin, as many overhangs have a sloping vertical. I have a lot of customers with 6.5/6.6 beds and with the max turn 5th wheels that do not want the slider, so Im trying to clarify the measurements formula. I also speak about dippinginch and tight turns at sites, etc., in addition to normal driving, as to the usefulness of a slider with a short bed. Thanks

asked by: Chris

Expert Reply:

Sounds like you are asking about the A parameter of the following formula:

(A + B) - C = Clearance

A = Distance from center of fifth wheel hitch jaw to truck cab
B = Length slider range/Sidewinder arm
C = Width of trailer divided by 2 (to get half)

You have to measure from the center of the king pin and not from the front of the trailer nose in relation to the king pin. The reason is that the king pin is where the trailer pivots. It does not pivot from the front of the trailer. Even with a super long extended pin box the pivot point still brings the trailer up to the cab when turning since when at a 90 degree turn the extended pin box now extends to the side instead of out back.

One solution for your customers with a short bed is to replace the pin boxes of their trailers with Sidewinders. You would have to know what pin box they have on their trailer currently to pick out the correct one. If you check out the help article I attached you will see a chart that shows this at the bottom.

The other solution is an auto-slide fifth wheel hitch like the Demco Hijacker # DM8550034. This hitch will automatically slide back as you make tight turns which eliminates the hassle of having to manually slide the hitch everytime you enter/leave a parking lot. This is a great option that we recommend highly.