Frame flex

I had an '04 Cruiser for 7 yrs w/o flex issues. But CR, like other brands changed to a notched frame for greater turning angle. My new Cruiser had plenty of flex, about 1-1/2 inches, that was 1-1/2 inches of travel at the pin before the landing gear started to lift. CR and Lippert repaired mine under warranty when the unit was 6 months old.

Frames do need to flex, especially given the road and campsite conditions that RVs experience. However, the trailer body also is attached to that flexing frame and as those attachment points get wallowed out (hard to make good steel to aluminum connections), then the frame flexes even more. If you are lucky, you may just have steel or weld failures, but you may also have more difficult problems to fix.

Here is a link to my frame, while it dealt with an inadequate design change, it may be helpful. repairFrame repair

In response to your post Denny, I felt that in order to get a true measurement of deflection, I needed to have solid points. Once you raise the pin to get the landing gear off the ground, without blocking, you get extra weight on the springs causing the trailer to move lower at the axles, so the geometry changes. I suppose, I could have blocked it just in front of the axles rather than blocking mid-way the axles and the deflection would have been marginally less. In any case, I think fixed points give you a better idea.
Today, I dropped the fascia to get a good look at the pin box, welds and structural members that the pin box is attached to. Very little movement there when I move the pin up and down and all the welds look sound. No blocking this time, I jack the pin 1 3/8 to get the landing gear off the ground. Now I do another experiment and raise the landing gear to get the pin off the jack. To do this, I raise the landing gear 3/4 inch. This tells me that half the problem is between landing gear and pin and the other half between landing gear and rear axle. I am coming to the conclusion that everything is intact, but that the structure is not built solidly enough. I am also coming to the conclusion that it has always been like this, although maybe not quite as severe.
Makes me wonder how many rvs there are with inadequate frames.
One thing I want to do before I conclude this lengthy post and that is to blast Lippert. Almost all the problems I have had with this trailer have had to do with Lippert. Broken shock mounts, uneven tire wear and a flimsy frame. My axle issues started with uneven tire wear. First I was told by the dealer it was the affected tires, and then he replaced them. Finally just before the expiration of the 2 year warranty, it was determined that it was an out of spec axle and it was replaced under warranty by another rv dealer. Then they couldn't get adequate money from Lippert so they came after me for the balance. Fortunately, Crossroads came through for me. After all this, the uneven tire wear problem was not solved. Took it to a truck alignment shop and for $100 my problem was finally sold. Anybody out there wanting to buy a new trailer, do yourself a favor and check who the manufacturer of the frame and axles is. I don't understand that there isn't more quality control. It's like building a nice home on a crappy foundation. That's my rant for now.

I see you have a LB truck. IF the 5er has an extended pin box, swap it for the short box. I've done that on 4 of my 5ers (including this one) and I put marks on the side of the boxes to measure the difference and the short boxes cause 1/2 the flexing of the ext. boxes. Craig

Lots of difference in the engineering and approach to how you design a bridge and an RV frame. A lot of the same design goes into either one, but they are different.

An RV frame has to flex, but they have be designed to flex in certain areas and not at the cutouts for the slides.

Ken

Being it's a Lippert frame I'm sure you may find some problems, there's a lot of threads on how to make repairs and it's normally not all that expensive in you can do some of the work yourself. I'm not sure what kind of wall framing you have, aluminum or wood but there are ways to get the scews to hold after you get your flex under control. The wall framing will not stop your frame from flexing, I know Nu-Wa thinks they can but it doesn't work for long, my trailer is 12.5 years old (a NuWa) and I it's been flexing for the last 10.5 years after the glue in the wall let go. It moves between 1/8 to 3/16 of a inch from hitched to unhitched.

I ran this by my nephew ladt year who's a engineer, he's the president of a marine engineering company that builds bridges and he says that any steel framing has to flex and it its designed properly and the right steel is used it will fex for many many years before it fails like our Youngs welding frame, I think it a Lippert frame is reinforced it will also last for years.

Denny

I'd still look at the frame. I bet you find some cracks or broken welds. It's the most common reason for frame flex. Even if it's a $2700.00 repair that's cheaper than a new trailer. If it isn't fixed how do you sell it or use it?

B.O.

Harry, we had a Cameo that was getting some flexing at the area forward of the bedroom slide corner. Water had gotten in and weakened the structure. The repair was to stiffen the area around the slide cutout. The repair was done by Kansas RV Center in Chanute, KS and was about $2700.00

The trailers that use the laminated side wall construction depend on the glue and sandwich construction to provide strength. Once water gets into the wall, the Luan plywood lets go and the wall looses strength.

SO just dropping the over hang bottom and adding metal may not cure the problem and will require a sidewall repair as well.

You need to decide if the expense of the repair is worth it on a trailer of the age of yours.

Ken

First why did you block the frame, you just added more weight to the pin. The axle weight is spread out over both axles starting at the from spring mount and ending at the rear mount. Do your experiment again with the axles taking the weight and see how much movement you get. I would drop any covers and inspect the frame for any damage and do your experiment with it exposed. You don't need jacks and blocks just put a 4x4 under the pin and use your landing jacks to take the weight on and off the pin. It you have any damage a good welder will be able to fix it, some movement it to be expected. I'm not defending Lippert their reputation is not the greatest but what you did was take about half of the axle weight and transfer it to the pin.
Denny

Google "fifth wheel pin box failure", or cracks, damage, etc. and there is a lot of info. on this. More common problem than you would think. Better do an inspection and repair as needed before it's too late.

We've experienced a serious Lippert frame issue before, but not on a FW. They continue to build TT & FW frames that are structurally inadequate and poorly put together. The real problem is the total lack of any industry standards and they can build whatever they want, however they want without answering to anyone.

The best thing to do would be to take it to a frame & axle shop that has a lot of experience with RVs. In BC we have gov't "designated inspection facilities" who have to meet gov't standards. If you have that in Ont., I would take it to a frame shop that has that also.

It has a bedroom slide. The sidewall below the front corner of the slide has been cracked for at least 5 years. Without looking at the trailer which is in storage right now, I would say that is about a distance of 6 in. I covered this with a small piece of eternabond to prevent water damage. The trailer sits fairly level over the truck, so I am thinking the problem is in the pin box area. Also, this didn't just happen but I think the severity has increased. One thing I don't need is a total frame failure in the dead of winter on the way to Florida. I will bring it home and open the bottom up to have a look and keep you guys posted. Thanks for the input so far. This is a great forum for learning and problem solving.