Cab to trailer clearance
I have a CC 6 1/2' box Silverado 2500HD. The pin box on a fifth wheel I am looking at is 12 inches in front of the trailer front cap. Is there a formula to see if I need a slider hitch.
Forum Discussion
Here is a simple formula for a simple example. King pin in line with the front of the fiver with a flat front cap. Distance from the truck cab to fiver, say 42 inches. Half the fiver width, say 48 inches. Then the max angle is the inverse sin of 42/48 or just over 61 degrees.
When the two distances are equal at say 48 inches, then the max angle is 90 degrees. Beyond 90 degrees, then 1/2 the cab width (which is about 35 inches) becomes a factor. I don't think I've ever seen an extended pin box with the king pin actually 12 inches in front of the fiver. But in that case, max angle becomes 90 degrees plus inverse sin of (52-48/35), which is about 6 degrees, for a total of 96 degrees.
Since most truck cabs and fiver caps have at least some curvature, side-to-side and vertical, actual angles will be greater than calculated by a small amount.
If the fiver front cap is notched, as most are today, then much more detail is needed about size, location and angle of the notch.
While all of this may be interesting, the more basic question is how much angle is needed? 60 degrees is more than the average TT can be jack-knifed w/o the trailer hitting the truck's rear bumper. If you are willing to take the time with extra maneuvering, then 60 degrees is fine. I had a non-slider for 14 yrs and never had a problem and the slider I have now hasn't been used in 7 yrs.
When the two distances are equal at say 48 inches, then the max angle is 90 degrees. Beyond 90 degrees, then 1/2 the cab width (which is about 35 inches) becomes a factor. I don't think I've ever seen an extended pin box with the king pin actually 12 inches in front of the fiver. But in that case, max angle becomes 90 degrees plus inverse sin of (52-48/35), which is about 6 degrees, for a total of 96 degrees.
Since most truck cabs and fiver caps have at least some curvature, side-to-side and vertical, actual angles will be greater than calculated by a small amount.
If the fiver front cap is notched, as most are today, then much more detail is needed about size, location and angle of the notch.
While all of this may be interesting, the more basic question is how much angle is needed? 60 degrees is more than the average TT can be jack-knifed w/o the trailer hitting the truck's rear bumper. If you are willing to take the time with extra maneuvering, then 60 degrees is fine. I had a non-slider for 14 yrs and never had a problem and the slider I have now hasn't been used in 7 yrs.
