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Topic: Bumper to trailer minimum distance - 5th Wheel

Posted By: rescuenatalie on 11/15/09 02:46pm

Hi. My new F450 pickup truck has arrived, and I backed it under my (also new-to-me) 2005 34' fifth wheel RV for the first time yesterday as I begin to make plans for hitches, etc. My general plan is to install an under-the-bed gooseneck hitch on the truck, and a 5th wheel to gooseneck adapter on the trailer. The truck has a long bed and DRW.

Whether I choose to go with a gooseneck or fifth wheel hitch, I have to be concerned about clearance between the rear bumper of the truck and the trailer. With the kingpin centered over the rear axle, there is only 13 inches between the outside corners of the rear bumper and the trailer. I expect that once the hitch is installed the kingpin will be just forward of the rear axle by a few inches, and bumper/trailer distance would be 10". I'm certain that isn't enough distance. What is the minimum bumper/trailer distance rule to eliminate clearance problems?

To solve the problem, I could install a longer pin box, or an offset gooseneck ball, or an offset version of the 5th wheel to gooseneck adapter. Any thoughts? Thanks.

Posted By: Fisherman on 11/15/09 02:54pm

First time misread, park the truck under the RV at about a 45 degree angle and see how close the centerpoints match. Then you'll see how much clearnace you have between bumper and trailer.

Posted By: Dr Quick on 11/15/09 02:56pm

I would measure the distance from the anticipated pivot point in the box, to the corner of the bumper at the edge of the vehicle. Then I would use this distance to measure from the trailer pin to the front of the lower overhang. directly back, then add some inches for insurance.

Dr Quick

Posted By: Golden_HVAC on 11/15/09 04:26pm


I would put a piece of electrical tape on the center of the bed, 1" forward of the rear axle, where the fifth wheel pivot point would normally be located.

This is your target for the center of the hitch to end up. The trailer needs to stretch to this point, and the truck needs to be at least 4" ahead of the fifth wheel during a 45 degree turn, so back the truck under the fifth wheel at a 45 degree angle until it is nearly touching the storage compartment door.

You will know how far the trailer hitch needs to go forward, to reach the tape on the pickup bed. Then get the right adapter to move the center of the hitch to where it is required to make a 180 degree turn while backing up.

However I might still suggest that a fifth wheel hitch will have a little more stability in crosswinds, and suggest that type of hitch be installed. Yet it is your truck, your choice.

Good Luck,


Posted By: Al B on 11/15/09 04:29pm

Adjust the pin box on the fifth wheel ahead to give you your clearance.

Cummins Powered

Posted By: WellShooter2 on 11/15/09 05:30pm

If the tailgate will open and close you should be good.

2008 2500HD D/A
2008 Keystone Challenger

Posted By: F-TROUP on 11/16/09 12:18pm

On my SB I had the hitch mounted 2" behind the axle and have had no adverse effects in towing and handling. You deffinently have the truck to handle the weight.

Posted By: johntank on 11/16/09 12:48pm

Try this; with a tape, measure from the king pin stright back to the trailer add 4 or 5 inches this will be the distance needed from the center of hitch jaws on a 5th wheel or center of gooseneck ball to the conner of your truck/bumper for clearance needed. I think that I have about 4" on mine. Hope this helps. John

Posted By: TXiceman on 11/17/09 10:33am

Next thing to do is to forget the Goose Neck Adapter. It will mostl likely void you frma warranty on the trailer.

In addition, it looks like an engineering disaster waiting to happen.
Use the search engine and you will find plenty of reading material.


Amateur Radio Operator.
2013 HitchHiker 38RLRSB Champagne, toted with a 2012, F350, 6.7L PSD, Crewcab, dually. 3.73 axle, Full Time RVer.
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Posted By: rescuenatalie on 11/21/09 09:01pm

Thanks, folks. You've made this clearance quesion easy to resolve.

Posted By: Miles Away on 11/22/09 08:36am

I have found that long beds allow less clearance between the rear bumber and the trailer. When I was towing G/N I purchased a four inch extender from B & W (I have a B & W gooseneck hitch), which moved the pin point four inches to the rear (slightly behind the rear axel) and it helped a lot. When I went to the B & W Companion on my new trailer I noted there is about four inches of fore and aft adjustment as well as about two inches of verticle adjustment. Your open tail gate clearance may still be tight, so you may want to opt for a 5th wheel tail gate or cargo net, which you won't have to open to hitch & un-hitch. The main concern is that your rear bumper does not hit you trailer when backing at extreme angles.

M & M "> On the road again!
2007 GMC 3500-SRW-Duramax-longbed-4X4
2008 Keystone EVEREST 348R 5th wheel
2002 SUNDOWNER gooseneck horse trailer

Posted By: 1100Sabre on 11/22/09 03:54pm

Use the GN adapter. It will not harm a thing. We've used them for over 20 years on many different 5th wheels and never have had a single issue.

2015 4X4 Chevrolet Duramax/Allison 3500HD Crew Cab SRW
2007 Sportsman Sportster KZ 33P Toy Hauler
"It's not the destination, it's the journey."

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