Towing a 5th Wheel Trailer with a Short Bed Truck Using a B&W Gooseneck Trailer Hitch

Question:

I believe there is a mathematical equation to determine where the king pin of a trailer is to set in the back of a truck. I am trying to decide whether to use a gooseneck adaptor or breakdown and accept a fifth wheel hitch. I believe you consider the width of your trailer, and with that number you can determine how far your king pin needs to be from the cab of your truck. On my trailer, it sort of vs out so there is a bit of the front that sticks further out than the king pin maybe 2 inches. The width of the trailer is 98. Based on my belief, my ball would need to be 49inch back from my cab. That would require me to get an offset for a gooseneck of about 12inch and I think that would be too much of an offset, if it is even offered. My question is: Is my equation correct, or are there other factors.

asked by: Jan K

Expert Reply:

You can determine where the center of the gooseneck ball would need to be (or the center of the 5th wheel hitch) based on the width of the trailer.

Take half the width of the trailer, in this case 98 inches, to get 49 inches. The distance from the truck cab to the center of the ball or hitch has to be at least 4 inches greater than this 49 inches to safely make 90 degree turns and to account for any dip or bumps when at that angle.

So really you would need 53 inches minus any distance from the center of the king pin on the trailer to the trailer overhang (if it sticks out past the front of the trailer overhang). If the king pin is recessed under the trailer overhang, let's say 2 inches, then you would actually need 55 inches cab to ball/hitch.

In an earlier question you mentioned that you have a B&W turnover ball hitch. You would need the Companion hitch, # BWRVK3400, which will give you an additional 12 inches of clearance from the truck cab to the center of the hitch. So using the math above you would only need 41 inches depending on where the king pin is relative to the front of the trailer.

There are no gooseneck adapters that offer 12 inches of offset.

expert reply by: Michael H