Cab to trailer clearance

John,

Not much to add to the discussion.... do remember that
calculations may not consider the effect of uneven/unlevel
ground when backing into your campsite, or trying to back out
of an oops ! turn. I have the 5ver nose indents on my AF
and the Reese Airborne ... I (slowly)put the TV thru 90
degree turns each direction (on level ground) and had clear
room from contacting the crew cab. Make sure your bed rail
clearance is in that 7 - 8 inch range, as 90 degree turns
really torque the 5ver wheels and can impact side rail clearance
if ground uneven. My 2500HD has the "standard bed".

I have not used the slider... but glad I have it.

Charles

The rule of thumb is minimum 48" from the center of the rear axle to the back of the cab for a standard fifth wheel hitch so the trailer will not hit the cab when turning.

This will take a long bed (8ft) pick up.

Traveler II wrote:

07PSDCREW wrote:
I don't know if you have a hitch already, or can borrow one if you already have the rails. I Meashured my trailers width and divided it in half. Then Meashure from the back window to the center of where the hitch would be in tow mode. If it is a lot less than the width of your trailer divided in half then I would get a slider.
Example. My trailer is 97" wide in front. Half that is 48.5". The meashurement between my aluminum back rack and the center of my hitch in fwd position is 36.5" So I bought a slider. I also opted for the Reese round tube as it had 12" of travel as opposed to the square tube 10"

For a rough estimate, you can judge just about where the center of your rear axle is under the bed of your truck, then go 1" inch or so in front of center towards the cab for your reference point. Most hitches run centered over the axle or just in front of it.
Good luck.

How would you calculate this is you have and extended pin?

.

It would be the same... The king pin is still in the middle of the trailer. Just with an extended pin box, you can turn further "before" having to slide the hitch.
The extended pin box will push the trailer back away from the cab a few more inches during normal maneuvering.
If you were at a 90deg, you would still have the same distance from the cab as a reg pin box. Your trailer would just be further away from the side of your truck.

Make sense?

duplicate deleted

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.

Does your 5th wheel have the corners "trimmed" at an angle or are the straight across the front of the unit. Some of the later 2011-1013 units hve trimmed corners and will not hit on most trucks. My 2010 Cougar DOES NOT have the trimmed corners and WILL HIT if I get in to more than a 60 Degree turn without sliding the hitch back. I habe a 2012 Duramax w/ext cab 2500HD with a curt 16K manual slider.

07PSDCREW wrote:
I don't know if you have a hitch already, or can borrow one if you already have the rails. I Meashured my trailers width and divided it in half. Then Meashure from the back window to the center of where the hitch would be in tow mode. If it is a lot less than the width of your trailer divided in half then I would get a slider.
Example. My trailer is 97" wide in front. Half that is 48.5". The meashurement between my aluminum back rack and the center of my hitch in fwd position is 36.5" So I bought a slider. I also opted for the Reese round tube as it had 12" of travel as opposed to the square tube 10"

For a rough estimate, you can judge just about where the center of your rear axle is under the bed of your truck, then go 1" inch or so in front of center towards the cab for your reference point. Most hitches run centered over the axle or just in front of it.
Good luck.

How would you calculate this is you have and extended pin?

not sure if you're measuring to the pin or the edge of the pin box. I just went out and measured mine and from the front edge of the cap to the edge of the pin box is 16" which puts the centerish of my pin at 12" ( eyeballed it) and I never have to slide my hitch. I think though the shape of that front cap will matter too.....not just the measurement to the pin box. I have an 06 duramax with the 6.5' bed.

Get a tape measure. Measure from the 5th wheel post on the trailer to the front left corner of the trailer. Then measure from the 5th wheel hitch post location to the driver's back corner of the truck cab. Bet the cab is closer on all short beds!

I don't know if you have a hitch already, or can borrow one if you already have the rails. I Meashured my trailers width and divided it in half. Then Meashure from the back window to the center of where the hitch would be in tow mode. If it is a lot less than the width of your trailer divided in half then I would get a slider.
Example. My trailer is 97" wide in front. Half that is 48.5". The meashurement between my aluminum back rack and the center of my hitch in fwd position is 36.5" So I bought a slider. I also opted for the Reese round tube as it had 12" of travel as opposed to the square tube 10"

For a rough estimate, you can judge just about where the center of your rear axle is under the bed of your truck, then go 1" inch or so in front of center towards the cab for your reference point. Most hitches run centered over the axle or just in front of it.
Good luck.