Frame flex

[Old Okie]

Originally Posted by Old Okie

Thanks for the guidance, guys! I wasn't expecting people loaded with YouTube videos, but they helped a lot.

Thankfully, I have no cracking or bulging issues on the upper deck sidewalls (or anywhere else) and we do have a king bedroom slideout up there. I haven't found any issues in the trailer or anything visible from the outside.

I did get the attached Lippert frame flex measurement pdf from their website, as I remember. However, it has no maximum allowable flex limits. I'd previously seen some folks saying the max was 1/4 to 3/8 inch. ChuckS, is this the measurement you referred to?

Thanks, again!

I intended to insert the frame flex pdf, but I can't seem to get that to work. The measurement is from the back of the hitch pin box diagonally down to the bottom of the trailer by the front landing gear on each side.

[Carl n Susan]

To add a PDF to your Post you have to click on "Go Advanced" in the Reply Box. The Advanced editor screen has a "Manage Attachments" button below the text box where you can locate and upload a PDF (or JPG or ?) attachment.

[Old Okie]

Thanks to Carl, I'm attaching the Lippert deck flex measurement diagram. ChuckS and twindman: Is this the measurement you were talking about? I haven't dragged the trailer out of the barn to make the measurements yet. I'm hoping they're negligible!

[MandK]

That’s the measurement I used, and the tail gate gets in the way. I had to put the truck at an angle to get an unobstructed line from the pinbox to the frame at the jacks. I didn’t feel like unhooking the tailgate. It sure used to be easier to remove the tailgates before all the cameras and sensors.

[Old Okie]

M&K,
When you did the measurements in accordance with the diagram, what kind of flex did you see? I assume you've seen no other problems.

Thanks for the reply!

[MandK]

Old Okie, I can’t remember the measurements exactly and they are written down at home and we are down south for the winter, but I want to say 5/16 and maybe 3/8”. I know the ods was slightly more than the ds and they were both within spec, Which meant that the frame was fine and that the problem was that the aluminum wall frame up front needed to be stuffed with wood and longer lag screws used to hold the walls to the frame. (I was seeing movement in the gooseneck area and the molding sealant was separating) My dealer was familiar with the problem. Once I measured it and confirmed it was within spec, I took the trailer to them and I had it back in less than a week. I got keystone customer service involved immediately and everything went very smoothly between keystone and my dealer.

[ChuckS]

Originally Posted by Old Okie

Thanks for the guidance, guys! I wasn't expecting people loaded with YouTube videos, but they helped a lot.

Thankfully, I have no cracking or bulging issues on the upper deck sidewalls (or anywhere else) and we do have a king bedroom slideout up there. I haven't found any issues in the trailer or anything visible from the outside.

I did get the attached Lippert frame flex measurement pdf from their website, as I remember. However, it has no maximum allowable flex limits. I'd previously seen some folks saying the max was 1/4 to 3/8 inch. ChuckS, is this the measurement you referred to?

Thanks, again!

Yup ( 1/4 ) inch movement is the MAX I would accept if it were my fifth wheel and preferably ZERO movement is what should be the case... I have ZERO movement

[Old Okie]

Thanks to everyone on my frame flex issue inquiries. I do appreciate your time and experience. As noted before, I don't have any issues with cracking or bulging of the filon exterior or movement/cracking of the caulked joints. However, that does not preclude problems with the steel framing underneath the body and its aluminum framing.

I'll do the Upper Deck Frame Flex Measurement according to the Lippert Sheet 0236 next time I have the trailer out of its barn, and hope for results like ChuckS's! If the test shows significantly more flex, you'll probably hear from me again!

Thanks again,
Old Okie

[rubio171]

Hello, can you tell me where you put your reinforcement? I don’t have any frame flex issues that I am aware of, I inspect all visible welds for cracking before every trip. I like to be proactive though and would like to maybe do the reinforcement before I have an actual issue. I do see some spots where the welds are only on one side of the shell beams, I have been thinking about welding them on all sides.

[Foldbak]

Originally Posted by rubio171

Hello, can you tell me where you put your reinforcement? I don’t have any frame flex issues that I am aware of, I inspect all visible welds for cracking before every trip. I like to be proactive though and would like to maybe do the reinforcement before I have an actual issue. I do see some spots where the welds are only on one side of the shell beams, I have been thinking about welding them on all sides.

Look at post 10 page 1 in this thread.

Frame flex occurs in several places. To my knowledge you cant install any supports without removing the side panels. ( Best left to the pros) The picture below shows the 2 most prominent places. Your rig should have a relief joint at the bedroom slide as shown in pic as 1. That's the most proponent place.

[Old Okie]

Hello gang,
I finally did the upper deck flex measurement on my 2017 Montana HC 305RL per the Lippert instructions. Absolutely, zero flex going from loaded to unloaded--which made me very happy! However, the hitch is moving relative to the front cap. From loaded to unloaded condition, I'm getting 7/16" of movement, measured from hitch vertically upward to bottom of cap. I talked to a Lippert Customer Service Rep after making both sets of measurements. He seemed to think the hitch to cap flex wasn't much of an issue, considering it was rock solid on upper deck to main frame deflection.

I'm not so sure, so I have a twofold approach:
1. I plan to take a few hundred mile trip with it, measure the hitch to cap deflection the same way when I get back to see if it's worsened or hopefully stable.
2. I did have Timbrens in place of the stock truck bump stops, which stiffened the ride considerably loaded (and unloaded). It also increased the impact load the trailer takes on a bottoming out situation, since Timbrens are designed for something like an 8000 lb load. It also seemed to bottom out more readily with the Timbrens, since they do reduce the travel of the stock springs before engaging. Granted, not as impact load as a full bottom-out on the stock bump stops, but this was rare. I've taken the Timbrens out for the above-mentioned trip hoping the "softening" of the rear suspension will allow more travel thus taking some shock loading off the trailer.

Truck is a 2015 Silverado 2500HD Duramax; trailer is a 2017 Montana 305RL High Country.