Hitch Question

forest376 · 11-06-2011, 07:17 PM

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Recently had a fifthwheel hitch reinstalled on a new truck. The new truck is taller and has a larger bed than the previous truck. Since my old truck had a small bed, an extender king pin bar was mounted on the fifthwheel. I lowered the hitch as much as possible. But when the king pin is in the hitch receiver, the bar is not level. The extender bar is higher in the hitch and lower towards the fifthwheel. It looks like there would be a lot of stress where the extender bar connects to the fifthwheel pin mount (since it is not level). I noticed there are 3 bolts that holds the bar in place. Now that I have a long bed, do you think I should just have the bar removed and go with the original default king pin? thanks

Jim W · 11-07-2011, 06:24 AM

Yes, you can go back to the standard pin box that was shipped on your 5er. Either you can reinstall the pin box yourself or have the dealer install the pin box.

I do have a question for you. What is the material is under the hitch rails? This looks like a piece of plywood, is it? Is the hitch mounted in the truck with this material under the hitch?

If it is I would have this material removed. The coefficient of friction is different between plywood and steel, than steel on steel. With this material under the hitch rail you are not getting the correct clamp load for the bolts to support the hitch against shearing. If you need a spacer of some type to raise the hitch, then use a piece of steel that will support the hitch correctly.

It is my humble opinion that the hitch and rails could move under an extreme load from the 5er in a panic stop.
Jim W.

W5WI · 11-07-2011, 06:37 AM

Quote:

Originally Posted by Jim W

Yes, you can go back to the standard pin box that was shipped on your 5er. Either you can reinstall the pin box yourself or have the dealer install the pin box.

I do have a question for you. What is the material is under the hitch rails? This looks like a piece of plywood, is it? Is the hitch mounted in the truck with this material under the hitch?

If it is I would have this material removed. The coefficient of friction is different between plywood and steel, than steel on steel. With this material under the hitch rail you are not getting the correct clamp load for the bolts to support the hitch against shearing. If you need a spacer of some type to raise the hitch, then use a piece of steel that will support the hitch correctly.

It is my humble opinion that the hitch and rails could move under an extreme load from the 5er in a panic stop.
Jim W.

I fully agree!

**JRTJH** · 11-07-2011, 07:47 AM

The compressability of steel is less than 10% of plywood, so in a high load/high torque condition (such as a panic stop or side maneuver) having 1/2 inch of plywood between the rails and the bed (actually the frame attachment posts) would be similar to having a 1/2 inch of freeplay (looseness) in the bolts.

I can't tell for sure if the plywood is actually "under" the bed rails or if it's 3 pieces of plywood laid around the rails. If it's under the rails, it's dangerous in a panic maneuver, if it's laid around the rails, it's dangerous as a flying object at 50+ MPH. Either way, it's not a good idea.

In fact, our installer was adamant that not even a co-polymer bed liner could sit between the rails and the bed surface. He said, spray on bedliner, paint or bare surface, nothing that would compress or act as a sliding surface.

I hadn't even noticed the wood on first glance at the picture. Good call !!!

SAABDOCTOR · 11-07-2011, 08:10 AM

YO WOOD IS FOR BUILDING HOUSE OR THE FIRE PIT NOT FOR SUPPORTING 10K LBS + OF 5ER! HOPEFULY YOU DID THE INSTALL AND NOT A DEALER

hankaye · 11-07-2011, 08:23 AM

Howdy All;

Noticed the plywood also took notice of the red cargo strap.
Appears the OP has the hitch "tied in" so that should be prior to the install. IMO.
Hopefully, the OP has removed the chunk of wood and has the hitch mounted as ya'll feel it should be (I agree, by-the-way).

hankaye

forest376 · 11-07-2011, 09:29 AM

Sorry about the mislead, that is cardbox under the hitch. I was on my way to CW to have it mounted. New question? My new truck has a standard bed 79 inches not a long bed. Can I still go with the original kingpin or still keep the sidewinder? I took several measurements, it would be close from the front of the 5er to the back of the cab. I read on a Reese site, the recommendation is 52 inches from the center of the hitch to the back of the cab. My hitch and bed would be closer to 42? I noticed last weekend, several trucks were pulling 5ers with standard beds....

forest376 · 11-07-2011, 12:47 PM

I called the service tech folks at Reese. I was told there can be some tolerance between the hitch and kingpin in regards to pitch/level. I may just have the sidewinder removed since I now have a Standard size bed...

hankaye · 11-07-2011, 01:48 PM

forest376, Howdy;

measure from the center of the king-pin to the front of the trailer, I do NOT know where they will mount the hitch in the bed of YOUR truck. It' a chevy...
Mine is a ford and the center of the hitch hole is 4" in front of the rear axel.
You can figure out how much "space" you will or will not have to spare.

hankaye

PS. almost forgot... (head-slap), do the measuring with the tail gate down AND up... better spatial reality

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