Trailer Frame Inspection - Where to look. (Picture heavy)

[JohnGB]

Fellow Sunline Club members,

This is a friendly heads-up informational post to urge you to add a camper frame inspection to your annual maintenance plan. Once you know where to look, the inspection itself will only take 10 to 15 minutes the first time. Less time the next time; this inspection is only a visual task and takes no special tools other than a flashlight.

This information can also apply to someone looking to buy a used camper or looking at one you own of any brand. I am not an expert on trailer frames, nor do I create trailer frames for a living; I am only passing along some of my findings as a goodwill gesture to help you keep your camper going for a long time. I have seen enough cracked RV trailer frames to see patterns in how they cracked, and I will present the findings on some of the ones I have seen so you can check your camper or one you are considering buying.

Please do not take this message as a “the sky is falling” warning that all used campers have frame issues, as this is not the case. The number of camper frames with failures in the big picture is low compared to the total number of campers on the road today, but frame failures happen. Many camper owners may have never considered inspecting their camper frame as part of annual maintenance; this topic falls into an out-of-sight, out-of-mind thing. Since this is a Sunline forum we are on, I will talk mainly about Sunlines. The last Sunline was built in the fall of 2006; come this fall, the last Sunline ever built will be 18 years old. We have many club members camping with campers older than 18, myself included. If you have a camper of any brand towed over 5,000 miles, consider adding an annual frame inspection.

You often can’t control the bad roads you end up on while traveling with your camper. Many campers do not have shock absorbers that tame down the excessive frame flexing. Towing over small or large bumps of bad roads aggravates and accelerates the camper frame flexing, which, in time, leads to metal fatigue that will start and continue to crack a camper frame as the miles add up. When you inspect your frame, if you find small cracks during the inspection, that is the time to create a plan for when and how to address the problem. Correcting it before the next camp may be necessary if you find advanced damage; if you do not know what it is you are looking at, look for someone to help you sort out when to get it addressed. After your first inspection, consider the follow-up inspections as an end-of-season activity. This gives you time to create a get-well plan if you find something before the start of the next camping season.

What I will present can also happen to other brand campers in the same common high-flex areas. This is an industry-wide issue, not just Sunlines. I have several friends with different brands with the same problems as the camper towing miles add up.

When campers are towed, the mileage accumulates. The more miles towed; the more flexing occurs in the steel of the camper frame. Flexing of the camper frame is normal and on purpose in most cases. Metal fatigue starts when the flexing metal stresses exceed the fatigue limit of the metal and design used in the application. A metal fatigue failure is an accumulative situation where the metal flexes back and forth to the point a crack “starts” in the metal. The design, manufacturing process, or the metal's exposure during the flexing cycles all play into the starting of a crack. That crack can take a long time in some cases and less time in others to get started, depending on several factors influencing it. Once the crack has started, the crack can increase in size more quickly with each normal flexing cycle of the camper frame during towing. As an example, if you towed the same low to medium annual miles per year, using the camper in the same manner, it may take 5 to 10 years in some cases to start a tiny crack and only 1 to 3 years for the crack to increase significantly in size, which in time, can lead to a metal failure.

Several factors influence the advancement of metal fatigue. Any factor alone can create metal fatigue; some may take longer or never show up while you own the camper. The next person who buys the camper may see the issue. The more combined factors, at the same time, can accelerate metal fatigue. Here are “some” common factors that can start a crack in a camper frame. Not in any order of importance, see how your camper stacks up to these factors:

1. Consider the number of miles the camper was towed since it was new. The 5,000-mile mark I discussed is subjective, but failures have occurred during this mileage period when combined with other factors.

2. The road or off-road conditions the camper was towed over. Smooth roads flex the camper less than rough roads or off-road travel. Unlike campers in a seasonal campground, campers with very little mileage may never experience metal fatigue.

3. The amount of cargo weight added to the camper. All campers have a weight rating; unless you have weighed your camper loaded ready to camp, you do not know if you have a lightweight load, at the weight limit, or over the weight limit.

4. The size and adjustment of a weight distribution hitch if one was used.

5. The amount of rusting/corrosion of the frame in high flexing areas.

6. The design of the trailer frame and the suspension system. The camper owner has no control over this; however, in the RV industry, trailer frames are considered a light-duty application compared to a construction trailer hauling heavy equipment used daily. The RV application has several specific considerations regarding the design process; some are lightweight, ability to handle the weight and size ratings, lower cost, lower duty cycle, towability efficiency, and a limited design life of the camper are all parts of the process. Engineers can design a camper frame that will not fail in a long-life RV application; however, the cost may not be practical for the average RV’er in terms of both RV cost and the size and cost of the tow vehicle to handle it.

7. Damage to the trailer frame. Damage can come in many ways, and some are; corrosion/rusting of the metal, overweight loading, mega-pot hole-laden roads, the frame being stressed by dragging it on the road driving out of a high-up gas station, and any impact or situation to the frame which creates high stress in the metal it was not designed to handle.

As you can see, all the above can be an everyday situation when towing your camper. I did not bring up the expected design life of a camper frame, as Sunline is no longer with us to ask that question. And I have not yet heard a tangible answer from any other brand camper. I can say that a maintained and repaired Sunline can last a good long time. Our 2004 T310SR, which we bought in 2007 and was built in November 2003, is now 20 years old, has over 50,000 miles we put on it, and is still going strong. Yes, I have done some major repairs and upgrades that are documented here on our site. If I maintain and keep repairing it, I can see it lasting another 15 to 20 years and another 50,000 miles. We have new members joining all the time, some with 30 to 40-year-old Sunlines. Age alone is not a factor; the seven items listed above are.

If you want to read more on metal fatigue, I found this steel supplier site with a simpler explanation of metal fatigue. https://www.metalsupermarkets.com/what-is-metal-fatigue/

And if you want a deeper techno-involved reading on metal fatigue, see here on Wiki. https://en.wikipedia.org/wiki/Fatigue_(material) Engineering websites delve even deeper into this.

Now, what to look for when inspecting your camper frame. I will try to do most of this with pictures so you can see what a failure looks like. I will do this in separate replies to make it easier to read. We have the intro post, which you are reading now; the inspections Part 1 A-Frames, part 2, the suspension area, and Part 3 and Part 4 are how some of the repairs or preventive reinforcements were done.

Some of you reading this post may do your first frame inspection and find the start of something with frame cracking or advanced frame failing. If you discover something, feel free to ask about it, take pics, and post so we can see what you have. We are here to try and help. You are also welcome to ask questions or comment about anything presented. We can all learn from each other.

I will first show a few pics with labels on several camper frame parts or areas. As the post goes on, these same labels will be used in discussion, and the pics will help show what we are talking about. You can ask about your camper using these terms so we know what you are trying to describe.

The following picture is from our 2004 T310SR, a 10,000# GVWR-rated travel trailer with a super slide (coach and dinette slide). Note: Most 8,600# and 10,000# GVWR Sunline travel trailers with I-beam style main frame rail campers were built like these pictures.

This T310SR camper is one of the larger Sunline travel trailers. The same frame principles exist in all the Sunline frames; they may be made from different sizes, steel grades, and steel shapes, but the overall design concepts are similar.

This camper's A-frame area is made from a 6” tall x 8.2 #/ft. C channel attached to a 10” tall frame header. Sunline used several steel shapes over the years to make the A-frame; some shapes were C channels in various sizes, rectangular tubing, or other shapes. Sunline used what is known as a “through header” design A-frame where the A-frame rails protrude through the header in most cases, unlike other brands, that attach the A-frame, which is made separately, and then is attached as a unit under the main frame rails and header.

Here is a typical Sunline-style A-frame. The A-frame area is one of the high areas of flexure of a travel trailer camper where cracks in the frame may exist.

The next area of higher frame flexing is the axle and suspension area that attaches to the wheels and tires. This 2004 T310SR is a leaf spring tandem axle setup like many, but not all, Sunlines. The pictures show the original Sunline suspension attached to the main frame rails. This camper uses a 10” tall x 9 #/ft. I-shaped main frame rails are often called an I-beam in the non-tech world. Technically, it is a thin RV beam, MH beam, in the RV and manufacturing housing industry, or M beam (miscellaneous), and it is not a true ASTM, I, or S shape beam. We will call it an I-beam for camper conversations. The main frame rails are welded to the main frame header by the A-frame area. The main frame rails have several cross supports (not shown) running left to right between the frame rails along the length of the camper. The rear bumper attaches to the back of the two main frame rails.

View looking under the camper towards the left side suspension system.

View of some of the main frame cross-supports. This model has an enclosed tank compartment, which traditionally only was supplied on certain models of the larger campers.

Here are some views of T310SR looking down the I-beam frame at the suspension area.

The view is looking forward from the left rear wheel area.

View of left side looking towards the back of the camper at the rear axle area.

This is a 2004 T-2499, 7,000 lb. GVWR non-slide tandem axle travel trailer. For this model and manufacturing year, they used a 5” tall x 6.7 lb./ft C channel as the main frame rails and the A-frame on a leaf spring suspension. As you can see, the main frame rails are made from different steel shapes, but the hangers, axles, equalizers, and shackles are very similar to the larger T310SR camper.

Not all 7,000# GVWR class campers used this C channel approach; some years used rectangular tubing for the main frame and A-frame. In the model year 2005, there was a frame redesign to change to 6” I beam main frame rails with 4” channel iron A-frames. This frame redesign in 2005 also changed the 5,500# and 6,000# GVWR travel trailers.

Many 2004 and older 5,000# GVWR class travel trailers used a 4” C channel main frame rails with a 4” C channel A-Frame.

Sunline also made many single-axle travel trailers and fifth-wheel campers with different combinations of main frame rails and A-frame or pin boxes. While there is a difference in the axle, suspension, and hitch areas, the trailer hitch area, the A-frame or pin box area, and the suspension area are areas of high flexure when towing. These are the main areas the frame inspection will be looking at.

More in the next reply on inspecting the A-Frame area.

 

[JohnGB]

Part 1, Inspecting the A-Frame area.

Trying to keep the wording shorter and not repeat things as much, I will talk about the areas of inspections with pictures of damaged A-frames so you can see some of the things to look for during an inspection. The reasons for damaged frames will be explained in detail later in the repair replies.

All areas of the A-frame need to be looked at during the inspection, which includes: (Suggest using a flashlight to see into dark areas as cracks do hide in the deep dark areas.)

1. The ball coupler. Look for any cracking in the welds of the coupler to the A-frame or bent/damaged coupler parts. Look up from the bottom at the ball latch area.

2. The A-frame rails, which start at the ball coupler, pass through the frame header and attach to the main frame rails under the camper. Inspect the entire length for signs of cracking or twisted shapes.

3. The frame header. Inspect the full width of the camper for damage where it is attached to the A-frame rails and for straightness. Take note of a bowed bend in the center of the camper.

4. The A-frame support angles create the battery tray. Inspect these battery tray angles for being bent/twisted open or upward/downward, indicating that the A-frame rails have been twisted excessively.

5. The LP tank mounting tray is attached to the top of the A-frame. Inspect for cracking of the welds from the tank tray to the top of the A-frame rails.

6. While under the camper inspecting the A-frame, turn and look towards the front axle, inspecting the main frame rails for any cracking or twisting of the top or bottom flanges of the main frame. A twisted top or bottom flange indicates that excess stress has been applied; even a small twist is a concern. Closely inspect the main frame where the cross supports are welded to the main frame rails for cracking of the welds.

I will start with a 2005 T-2363, which has a failed A-frame, almost to the point the right-side A-frame rails were broken free from the header. The camper has a 5,500# GVWR (Gross Vehicle Weight Rating), a 6” I-beam main frame with a 4” C channel A-frame, and the owner used a WD hitch. I was helping a camper friend inspect this trailer on a dealer’s lot who wanted to buy it. After finding water damage and the A-frame damage, combined with the dealer's unwillingness to lower the selling cost, they decided to pass on it. These findings are from Oct. 2017; the camper was manufactured in Feb. 2005 and was approximately 12 ½ years old. By the looks of the damage, I estimate the damage started roughly 3 – 4 years before and kept growing in severity. This is a very nice camper; I tried to acquire it as a project camper to restore, as it was perfect for restoration. However, the dealer wanted too much for it and knew they could sell it as is come spring. All this damage is repairable.

Here is the camper.

The first part of the A-frame inspection. I started following the left-side A-framer rail to the header and looked closely at the header joint. So far, this side looks good. While here, and I have no pic, I also look just inside the A-frame at this same joint while not yet under the camper. All looked OK.

Next up, go to the right side and do the same thing: start at the ball coupler and follow the A-frame rail to the header.

It's too dark; you have to look closer with more light.

Knowing where to go looking, ah yup, there is a problem. See if you can see it.

A closer look to the right of the white hex screw head above the top of the A-frame rail. The tell-tale of a crack is to look for a rusted witness line. The fresh exposed metal rusts along the crack line as the metal cracks and time goes on. When you see this, you know you have to dig deeper. NOTE: They do not all crack like this; this is an advanced crack this high up.

Now look for a bent header and battery tray angles.

The battery tray angles do not look bad; the header may have a slight bow in the center, but I can't tell yet.

Now it's time to crawl under with a flashlight and start looking from the back side of the header. This is a must, as you can see more of what is happening.

A scan to the left side.

Now, to start honing in on the right side of the problem area.

The header metal is cracked free at the bottom of the A-frame rail.

Look closer with more light.

A few things are wrong with this picture; see if you can find the three things.

1. A crack runs almost to the top of the header.
2. The header metal is cracked at the bottom of the A-frame rail.
3. To my surprise, they never weld the back side header tab to the middle of the A-frame rail? That header tab, which the web of the channel passes through, I "thought," is typically welded on both sides. In this case, I know the tab is welding on the outside, just not on the inside.

Let's look at the right side at this same joint.

NOTE: You are seeing the bottom header metal bend up to the bottom of the A-frame rail, where the channel extends through the header. This is normal; I have seen this on all the frames I looked at. They weld the bent-up tab to the channel, at least on one side.

Since I only found what looked like a missing inside weld on the right side from my pics last night doing this post. I now see the left side may also not be welded inside the header tab to the channel. It is just that this side is not flexed open like the right side is to see the split. If there is a weld on this left side tab, it is very light. There is a full weld fillet on the outside. A one-sided fillet weld does not have much strength when the joint flexes. I will have to dig into this more on my campers in the barn.

While under the camper, look back at the front axle and check the main frame flanges and cross-member welds for cracking.

Next is a 2004 T-2475, which had a buckled header and the start of a failing A-frame. This camper has a 5,500# GVWR, 4” C channel main frame with a 4” C channel A-frame, and the owner used a WD hitch. This is now one of my project campers; the owner did not know there was A-frame damage and had used the camper the prior session. These findings are from April 2018; the camper was manufactured in April 2004 and was approximately 14 years old when the damage was found. I estimate the damage started roughly 3 to 4 years before. This damage has been repaired, and we will talk about it in the repair post.

This camper has the same 4" channel A-frame rails but uses a 4" channel main frame rails. As such, the header is shorter in vertical height than the 2005 T2363 shown above.

This camper is undergoing restoration and is in the process of repairing the A frame. I will show highlights here as I do not have the step by step pics like on the T-2363.

Here is where we are starting from. This camper has a buckled header.

In the case of a bent/buckled header, I pull a string tight across the bottom of the header to see how good or bad it is.

I can measure the bow in the center. The header sections outside the A-frame rails bend down, and the header center can be twisted or not so twisted and bowed or not so. In this case, I have a 5/8" difference in the center.

Now, look down the bottom of the header, left to right across the camper.

Now, to look inside the A-frame at the header connection, the A-frame rail. This is still the outside area of the A-frame where the battery angles are.

The right side is buckled where the header metal joins the A-frame rail.

The left side is also buckled. And you can clearly see there is no weld on this side tab. The T2363 had welded on this side but not the inside.

Next are more pic closeups of the A-framer rail to the header, still not yet under the camper.

The left side joint. The header is cracked off the A-frame rail

The right side also cracked in this area.

Now to looking at the damage from under the camper.

Here is the left side. You can see the header buckled where it meets the A frame rail. You can also see they did weld the header tab to the A-frame rail, just on the inside this time. There is no weld on the outside. It appears they only do a one sided fillet weld. The convention on which side may be a change in the frame sizes. I will still look more into this.

Here is the right side. The same looks as the left side.

Some of our early club members may recall this post from July 2008 when club member Clarkdc asked about their 2007 T-2499 with a bent frame header. The camper has a 7,000# GVWR, a 6” I-beam main frame with a 4” C channel A-frame, and the owner used a WD hitch. This camper was 1 to 2 years old when the damage occurred and may be the most advanced damage the club has seen. This has all been repaired, and they are still camping with the unit. https://www.sunlineclub.com/forums/...cross-member-on-07-solaris-t-2499-a-9326.html

That post highlighted several other 2005 to 2007 campers from club members with the T-2499 once they knew to go looking. The T-2499 has a very high loaded tongue weight for its weight class, which accelerated the failures. We have not heard yet of any 2003 or 2004, T-2499s with A-frame damage. Those 03 and 04 model years utilized 5” C channel main frame rails with 5” C channel A-frame. The same type of 4” channel A-frame damage is showing up on other models; it has just taken longer, years’ worth in many cases, to be realized.

Here are a few pic highlights from that post from other members that I did not have pics of.

Bent battery tray angles and header

Another bent header.

This post by shepards2, is with a 2007 T-257SR, which had a totally failed header. The right side A-frame rail while still intact, completely broke free from the header. This camper has a 7,000# GVWR, an I-beam main frame (I am not sure if it is a 6” or 8” I beam due to the slide) with a 4” C channel A-frame, and the owner did “not” use a WD hitch. He towed it with a 1 ton Dodge dually. The camper was built between mid-2005 and October 2006. The damage was reported on Sept. 2021; the camper was approx. 16 years old with a reported estimated 20,000 miles. https://www.sunlineclub.com/forums/f63/catastrophic-failure-of-hitch-a-frame-beams-20258.html

I know of another 2007 T-257SR from a club member, which had a buckled header and the start of a failing A-frame rail separating from the header. He had just bought it used and had not yet towed it to camp. I saw the damage myself in his driveway and pointed it out to him so they could fix it. It was repaired, and he used the camper until he bought a new one. The damage was found in April 2018; the camper was approximately 12 years old.

Last summer, while camping with other Sunline friends, I found a friend’s 2003 T-2363 with a very broken frame header, which he bought used a few years back. This camper has a 5,500# GVWR, 4” C channel main frame with a 4” C channel A-frame, and the owner used a WD hitch. The entire mid-section of the header was separated from the A-frame rails. He had no idea this damage was there. What saved him from being able to tow the camper was that he created a large battery holding rack across the top of the A-frame, had parts of it welded to the outer parts of the header, and bolted to the A-frame rails. This battery tray helped add rigidity to the A-frame in place of the header. He has now had the A-frame repaired and is using the camper again.

If any of our club members find A-frame issues, please post here on this thread so we can help keep them all in one location.

In the next reply, we will see the inspection of the suspension area.

 

[JohnGB]

Part 2, Inspecting the suspension area and main frame.

I will talk about the areas of inspection with pictures of damaged main trailer frames so you can see some of the things to look for during an inspection. The reasons for damaged frames will be explained in detail later in the repair replies.

All areas of the main frame system need to be examined during the inspection, including: (Suggest using a flashlight to see into dark areas.)

1. The main frame rails, both the left and right sides, the entire length of the camper. Depending on the frame style, C channel, I-beam, rectangular tubing, etc., does not matter; all frames need to be looked at for cracks in the metal or welds. Look over both the outside, inside, and under the frame rails.

2. Special note for campers with I-beam style main frame rails. Check the I-beam's top and bottom flange for distortion (bending) along the entire length of the main frame rails. Most of the frame rails’ strength is carried by the top and bottom flanges being straight in their original position. Distortions can include a slight or significant bend up or down of any part of the top or bottom flange or, worse, a crack in the top or bottom flange. Make a heightened inspection at spring hangers or axle subframe mounting frame area.

If you have experienced a very rough, bouncing road to camp, check the lower flanges at the leaf spring hangers or the torsion axle subframe area if equipped when you get to camp. If you find any bending in the frame flanges, keep an eye on it and get it checked out soon. If the flanges have a significantly bent lower flange, it indicates the potential of a weakened frame rail due to a prior event. The camper or frame may not look that bent right after the bad towing event. However, if the flanges are damaged, the frame rail is weaker than before the event. Going forward, when normal towing mileage increases, the frame keeps flexing, and damage can/will continue to increase, even on regular roads, creating significant problems later. Not correcting the bent flange within 500 to 700 miles after, can make for a much more extensive repair if the flange is bent bad enough.

3. The suspension area has a higher probability of cracking or bending and should take extra time for inspection. The tires may be in the way to see clearly; use a flashlight for added lighting. On leaf spring suspension, check the hanger welds for cracks where they attach to the frame, signs of bent hangers, and cracks in the main frame web steel near spring hangers. On a torsion axle suspension, check the subframe for weld cracks to the main frame and where the torsion axle mounts to the subframe.

4. The main frame cross members run left to right of the camper along the length of the main frame rails. Look for cracks at the weld connections of the cross members to the main frame rails.

5. Check the rear bumper mounting metal for weld cracks where the metal mounts to the main frame rails.

6. If your Sunline has a freshwater tank under the camper, check the support angles under the fresh tank for bending the support rails. This is most important on I-beam style frames. (More on this in the next reply, talking about specific model issues)

The inspections may seem like a lot, and it can be the first time you have ever done this. Part of the main frame inspection can be combined with the A-frame inspection when you are under the camper. Everything is new to you, and you may be unsure what to look for. Ask questions, take pics, and post, and we may be able to help. Each time you do an inspection, you will improve, and the task will be faster.

What you will see in the pictures are mainly I-beam-style damages and cracks. These cracks are not only a Sunline issue; they exist on many other brands of these styles of frames, including many new campers above a 3,500# GVWR. The Sunlines may have fared better than most. Regardless of the style of the frame, the inspection is done similarly. On the Sunlines, the heavier campers with the I-beam web cracks show up sooner/less miles than the smaller campers. The heavier camper weight can stress the frame faster without added reinforcements, resulting in cracking sooner.

The first camper I will show is a 2007 T-286SR, which uses a 10” tall I-beam style frame on an 8,600 lb. GVWR camper. The mileage on this camper is not precisely known. However, my friend bought it new as one of the last Sunlines made. They did cross-country travel a few times, starting in Michigan and trips from the north to Florida a few times before these frame cracks were found in June of 2018 when I was camping with them. We had a campfire talk; I walked up to the camper, and yes, it had a main frame rail web crack problem. I pointed them out to him. They had no idea the cracks were there. A local welder has fixed them, and the camper is still being used.

I did not take pics of the cracks before they were repaired, so you cannot see the rust-stained crack lines. I did some restoration and axle work on this camper a year after the repair; here are the repaired pictures with circles of where the cracks were over the spring hangers in the I-beam web section. I underlined the crack weld in red so you can see the weld more easily.

Here is the overall axle setup on the right side of the camper. The red-circled areas show the web cracking.

Here is the right-side rear web crack.

Close up

Here is the right-side front web crack.

Close up

Here is the left-side rear web crack.

Close up.

Here is the left-side front web crack.

Close up.

The main frame web cracked at all 4 spring hanger locations. The 2 equalizer hangers did not show signs of cracking during this inspection.


This next camper is a 2007 Komfort brand travel trailer from one of my camper friends who lives in the northwest US area. I’m sharing these pictures with his permission as it helps us see the frame web cracking issue on the thin I-beam style frames used in the RV industry if they are not reinforced enough. He had a 2007 Komfort brand camper, a higher-end camper like Sunline, just made in Oregon instead of Pennsylvania. This camper has a 10,000 lb. GVWR is on a 10” I-beam style frame, like the Sunlines of the era. The crack damage was found in the spring of 2012. Their camping style included many boondocking sites requiring off-road travel to get to the campsite. Note: Komfort had a history like Sunline, making very good campers, and started from a small independent company. In 1995, Komfort RV was acquired by Thor. As reported on the web by prior owners, the older Komfort campers were liked better than the newer ones. In the 2011/2012 time frame, the Dutchmen division of Thor redesigned the Komfort campers and used the brand name.

The crack damage occurred as an I-beam web crack above the equalizer hanger. This crack was found relatively soon after the metal cracked. There was minimal rust on the crack line. It is tough to see in pictures until all the paint is removed during the repair process. The camper was repaired with added reinforcements and used without any future cracks in the 11 years following when he sold it, even in off-road conditions.

The camper up on jack stands ready for the repair.

The axle area. Something to note: Komfort did not have the angled web reinforcement at the equalizer hanger as Sunline did. Komfort used a V-shaped 1/4" plate between the hanger, and the ends were welded to the bottom of the main frame rail. We will talk about this more in the repair reply. Both reinforcement methods have been shown to fail and crack the web. This picture is during part of the repair process, it is used to show the over all suspension setup.

Here is a closeup of the equalizer hanger web crack. In the picture, it is hard to see the faint crack line with some dirt and paint in the area.

Here is the cracked area after the wire brush treatment to prep the surface for welding.

Here is the crack during part of the grinding process during the repair.

The next camper is a 2005 T-1950 with 6” tall I-beam style main frame rails rated at 5,500 lb. GVWR. This camper has been in full-time use across the US annually for the last nine years. The towing mileage by the prior owner is unknown. Most all towing is on over-the-road conditions in established campgrounds with hookups. These cracks were found when I did axle work for my friend in October 2022. This cracking follows the same pattern as the larger campers; it just took longer to show up.

Here is the right-side suspension setup. The prior year, a dealer installed the Dexter HD shackle kit and greaseable bronze bushings.

At this time, only the front right and left spring hanger areas had web cracks. The rear spring hanger or the center equalizer hanger did not have any web cracks.

The front right web crack. It was easy to see during the axle removal. The camper was getting an axle under/over conversion (aka axle flip) to gain more ground clearance.

Here you can see pics of the rusting witness line to look for.

This right front hanger area web crack happened at a cross support member. Here is inside the frame at the crack location. You can also see the LP gas pipe clamp cracked off. I an unsure if the pipe clamp crack came from the frame flexing/twisting or not.

A close up pic.

Here is the left front axle area. The frame web cracked at the same cross member as the right front side. It also had a web frame crack at the outrigger support forward of the front axle.

The left front cross member crack.

Inside the frame of this left front axle web area crack, it is the same cross member that cracked on the right side

Here is the left outrigger support that holds up the outer left wall to the main frame rail. The crack is at the very bottom of the outrigger bracket.

Here is the inside of the outrigger crack

This link will take us to a 2005 T2753 with a 6” I-beam main frame rails and a 7,000# GVWR.
https://www.sunlineclub.com/forums/f71/2005-sunline-solaris-2753-crack-in-i-beam-20493.html

Club member, flbradjr, Brad found I-beam web cracks near the center equalizer hanger and in the cross members where they attach to the frame rails in August 2022.

Right side of the camper web crack above the equalizer hanger.

The same web crack inside the frame at the cross support member.

The left side of the camper, web crack above the equalizer hanger.

Hard to see, but inside the frame at a cross support member. The flashlight is pointing to it.

See Brad’s post for more pics and info.

The next few pictures are from a 2007 T2499 with a 6” I-beam main frame rails and a 7,000# GVWR. We were camping with one of our Sunline friends, having a campfire chat. The topic of frame cracks came up, and we walked over to their camper. Yes, they have web frame cracks, that had not realized before.

The left side main frame web crack above the equalizer hanger.

The right side main frame web crack above the equalizer hanger.

They also have a leaf spring and equalizer issue that I noticed when zooming in on these pictures. I will alert them of this. The rear leaf spring is also bending the bottom flange of the main frame and the front leaf spring is hitting the equalizer hanger.

Next is a bent spring hanger on our 2004 T310SR. This camper has a 10” I-beam frame rated 10,000# GVWR. The bent hanger was found on May, 9, 2009 when doing suspension work. The towing mileage has been approximately 4,000 miles since we acquired it in September 2007. The milage by the prior owner is unknown, but I can tell by the lack of wear and use, this camper was not towed much by the prior owner. The bent hanger was straightened and reinforced; more on this in the repairs reply.

You and see the bottom of the hanger is bent inwards by 7/16". This is not normal.

On the same camper, our 2004 T310SR is a bent lower frame flange behind the left rear axle spring hanger. This camper has a 10” I-beam frame rated 10,000# GVWR. This is a major deformation (bending) of the lower flange rendering the camper unusable in this condition. I’m sharing this detail so we can all see and learn from it. I was not doing annual frame inspections at the time until I learned the hard way, how bad, bad can get if small things are let go unnoticed or repaired. Trying to create a timeline of the damage, I backtracked my pictures. Here is a timeline leading up to the significant issue.

1. Some small event or events, not known at the time, occurred in late 2009 or early 2010. By December 2010, a picture review showed a slight deformation of the lower flange behind the left rear axle hanger—my towing mileage lines up with approximately 11,000 miles at this period.

2. In 2012, I had to readjust the slide room to work correctly as the slide opening in the camper started to become out of square. The left main frame rail was slightly bending downward, creating this issue. The towing mileage at the end of 2012 was approximately 17,000 miles. After the slide adjustment, the slide worked OK and continued camping.

3. On July 24, 2014, we headed out of Albany NY, down I-88 to I-86 to camp at Watkins Glen SP on the lower end of Seneca lake. The towing mileage at the end of 2012 was approximately 21,000 miles. During this I-88 road stretch, what started in Albany as brand new black top interstate, ended up with the last 15 to 20 miles of mega pothole concrete road. The road had no pull-offs until a rest stop to escape this pothole interstate. I slowed to 50 mph in the right lane, semis whizzing by doing 70 mph for the last 15 to 20 miles. What the truck tire track missed; the camper tires hit dead on at highway speeds. When we made it to camp, everything in the camper was tossed around. The swivel rocker in the back of the camper stowed upside down for travel landed right side up and put a big ding in the side of the slide room siding. This event, now looking back, started increasing the lower flange damage by orders of magnitude.

4. By the end of October 2016, the left side main frame rail had bent down far enough, the slide room no longer would work or could be adjusted to work without damaging the slide roof going in or out. The camper was no longer usable in this condition. Mileage at the end of October 2016 was 24,760 miles, 3,409 miles since the mega pothole ride on 7/24/14. The camper underwent major frame repairs and reinforcement, and we continue using the camper today, where we are at the 50,000-mile mark. More details are in the repairs reply.

Here are pictures of what normal flanges look like before the heavily damaged lower flange. The bottom flange behind the hanger is straight and true.

The shock absorber was a test fit that was never mounted outside the frame, they where inside the frame later on. The picture is to show the normal condition of the lower frame flange behind the rear axle spring hanger.

As FYI, when the slide is adjusted correctly and there is no main frame damage, the ends of the slide room flange gaps are parallel with camper opening wall flanges as shown in this picture. This is not intended to declare a bent frame if the slide flange gaps are not parallel, this can also be caused by a misaligned slide drive.

Here is the start of a lower flange bend. It is very slight in 2010 caused by some unknown event. This was the time to reinforce this slight bend. I was not educated enough 13 1/2 years ago on how critical these thin I beam flanges have to be held in true location to handle the stress of towing a heavy camper. Live and learn, we all do.

Here are pictures from the 2016 time frame trying to sort out what went wrong with the left main frame rails. There was very slight deformation on the lower flange on the outside of the frame. I added hanger support reinforcement a number of years before to be proactive and not have web frame cracks. That hanger reinforcement helped the outside flange, but not enough to help the inside of the lower flange.

Here is the inside behind the left rear hanger. This is the major damage.

If you see this, this is a problem.

The last is a 2007 T2499 with torsion axles where a subframe is welded to the bottom of the 6" I-beam main frame rails. This camper is rated at 7,000# GVWR. Club member EMAM and his wife travel the country with their Sunline. There axle mounting had bent metal and cracks.

See their post here, with more pictures and the resolution. https://www.sunlineclub.com/forums/f71/axle-frame-cracks-on-our-2499-a-9812.html

I hope all this helps give you some insight on what to look for when inspecting your camper frame.

Thanks

John

 

[JohnGB]

This reply will be for extra frame areas to inspect on specific years and models. There may be other years and models with specific repeat damage patterns; the ones listed here are the ones I know of. If other club members report their findings, we can help expand the list of unique frame issues if enough repeat patterns occur.

NOTE: Do not misunderstand that these models “all” have these issues, as this is not the case. From our limited info, these models seem to have a repeat pattern after enough towing mileage and road conditions have accelerated the metal fatigue. All the damage found can be repaired.

Model: T2363, model years, 2005 through 2007. This 5,500# GVWR camper had some design changes during the 2005 model year, which included:

1. Changing the main frame rails from 4” C channel to a 6” I-beam. All 5,500# and 7,000# GVWR campers had this change.
2. The freshwater tank was moved from under the bed “inside” the camper to be located “outside” and hung off the main frame rails under the camper in the same general area floor plan-wise as the tank was in before.

Two T-2363 campers were reported here on the forum with unique damage associated with the floor plan—and at least one, 2007 T2753.

This post by member beecrazy (Don) shows their 2005 T-2363. https://www.sunlineclub.com/forums/f71/bent-potable-water-frame-13295.html#post101020

The report in 2012 was a bent fresh tank support angle next to the rear axle hanger. Don bought the camper used, and he found the problem soon after acquiring the camper. We know it was 7 years since the camper was made, unknown is how many miles the prior owner(‘s) towed the camper and under what conditions.

Here is Don’s bent tank angle.

During that post, member Tweety reported that their 2006 T-2753 also had both tank angles bent, and they have the new 6” I-beam frame. Their tank is in front of the front axle but close to the spring hangers of the front axle. Using the I-beam style main frame, this issue may appear on other floor plans with the fresh tank under the camper and near the front or rear axle spring hangers.

The next 2005 T-2363 I am reporting in this post. In 2022, I inspected a 2005 T-2363 for sale at a dealer for a camper friend. That camper was found to have a damaged A-frame, as I reported above in the prior post. While reviewing the limited pictures I took during that inspection, I saw that the camper had the same bent tank angle behind the rear axle hangers as beecrazy reported. Pictures of the main frame cross member at the equalizer hanger area were also found, where the lower parts of the cross member were cracked and separated where it attaches to the main frame rails. I did not find this during the 2022 inspection; I found it while reviewing pictures for this post on the cracked frame header a week ago. I have limited pictures from the 2022 inspection and no knowledge of who bought the camper from the dealer.

This is the third camper reported on the forum with these bent tank angle issues when they are directly next to an axle spring hanger. I see a possible pattern of how this damage may occur with the 2005 new I-beam style frame. I am unsure if this damage happened on the older style frames. I will report on this in the repairs post. I want to state that not all T-2363s have this issue. I restored a 2005 T-2363 in early 2019 for a good friend, and their camper did not have this damage. They bought the camper new, and their camping trips had lower mileage to the campsite.

Here are the pictures of the damage from my inspection.

Bent fresh tank angle by rear axle hanger. I drew in a straight red line to help show how far the bend is.

There is a possible web crack at this outrigger support. This is my only picture of this area—the rust witness line is a characteristic of a cracked web section.

A buckled and cracked cross member on the left main frame rail.

Here is a close-up showing the damage. Sorry, the pic is so fuzzy.

Here is a clearer picture of the right-side cross-member weld to the right frame rail. On the bottom, the cross-member buckled and cracked loose from the frame.

A closeup

I have seen Sunline use this style of cross-member on many of the pre-2005 I-beam frames. They continued to use it when they went to the new I-beam frame design. It is a Z-shaped profile cross member. Here, on the front part of this same 2005 T-2363, you can see what a non-bent cross member looks like. There is low side stress in the frame in this area and no buckling of the cross member.

This is a close-up. The cross-member is notched to fit over the top of the frame, and in older frames, the Z cross-member could also be reversed; the lower cutout would then be on top.

Model T-1950: The damage was found on model years 2005 through 2007. This 5,500# GVWR camper had some design changes during the 2005 model year, which included:

1. Changing the main frame rails from 4” C channel to a 6” I-beam. All 5,500# and 7,000# GVWR campers had this change.

NOTE: The T-1950 model has a unique left rear main frame rail jog, which is required due to the left rear bathroom and how the black tank drain piping is routed. The jog starts as a 6" I-beam short after the rear axle spring hangers and then jogs outwards with a 3" channel iron cross member, then turns 90 degrees and extends to the bumper mount with a a 3" channel. This frame feature is unique to the T-1950 floor plan. The T-1950 floor plan was popular, made many years before the 2005 main frame redesign. It is unknown if the T-1950s made before the 2005 I-beam frame change have the same frame issues. The recommendation is to check the jogged area behind the rear axle for frame cracking, as shown in these pictures.

This picture from a 2004 T1950 helps show the frame jog. The 2004 T-1950 does not have the 6" I beam frame; it uses a 4" C channel frame.

Two T-1950 campers with the 2005 6” I-beam style frame have been reported on the forum as having cracked the main frame rails web sections on both the frame's left and right rear side where the frame jog area is located.

I have a 2004 T-1950 that has been restored. This prior-generation main frame rail is made from a 4” C channel. I inspected the areas in question and found no frame cracking at the frame jog. However, I reinforced the joint as a precaution. The prior owner told me they took the camper cross-country twice. I do not know the total towed mileage or the road condition it was exposed to. I will report on the reinforcement I did in the repairs reply.

Club member Tod Osier, with his 2006 T-1950, was the first to report the issue in 2020. See Tod’s post here with pics. https://www.sunlineclub.com/forums/f71/t-1950-frame-repair-suggestions-needed-19648.html

The issue is that the frame jog flexing, combined with the rear axle turning stress in the main frame rail, cracks the main frame rail web section on the left rear side. If the towing mileage and road conditions are high enough, the cross-frame support in this area also cracks the rear right-side frame rail.

Here are two pics from Tod’s post to show the problem. This is the left rear frame jog area.

This is the right-side rear frame crack just below the frame outrigger.

After seeing Tod's damage, club member A Pack of Two (Joan) found the same problem on her 2005 T-1950 in August 2020. Joan was out of a reliable cell service area then, so I helped her to post her pictures. The thread is slightly out of the correct date order; here is the post with several pictures.
https://www.sunlineclub.com/forums/f71/frame-rail-cracks-19848.html

The left side frame jog area.

The right-side outrigger area.

NOTE: Both 2005 & 2006 T-1950 were towed cross country several times by their owners. Both campers are considered to have higher-than-average mileage. It is unknown how many miles and what road conditions either camper has that allowed this metal feature damage to occur.

Model T-1950 left rear bumper mounting bracket. The main frame design of using either a 4” C channel or a 6” I-beam does not seem to be a factor, with the left rear bumper mounting bracket having a cracked weld. The jogged frame to make the black tank drain piping work and possibly having the spare tire mounted on the left rear of the bumper may be factors in why this location cracks over enough miles towed. It is suggested all T-1950 owners be on the alert for the left rear bumper mount.

Here, the left bumper mounts on a 2005 T-1950 with the mounting plate cracked where it joins the jogged frame rail. This camper has a spare tire on this side of the camper. The water heater and rear cargo storage door occupy the center of the camper all the way to the right side.

The next camper is a 2004 T-1950 with a cracked bumper mounting plate.

The right side shorter bumper mounting plate had the start of a crack.

Both of the T-1950 with bumper mounting plates cracks, did cross country travel. The owners of both campers never knew there was cracks in these locations until forum members alerted them of where to look.

This ends the frame inspection postings. The next two section deal with how the damage occurred and some possible repair options.

 

[JohnGB]

Part 3 is held for A-Frame area repairs coming soon.

 

[JohnGB]

Part 4, Suspension area repairs.

This section is quite detailed, outlining the sources of suspension area frame damage and repair options. It’s all consolidated in one location, so reviewing it will take time. However, as needed, you can refer to each section as you work through your frame repair.

This reply addresses the failure modes and repairs of the camper's main frame rails in the suspension area, focusing specifically on trailers that utilize spring hangers with leaf springs or torsion axles employing I-beam style frames used on hard surface highway and county paved roads. We will not get into off-road backcountry towing as the way these campers are built they are not intended for large amounts of off-road towing. Sunline also manufactured trailers with C-channel or rectangular tubing main frame rails, which can also experience cracked welds or metal fatigue in the suspension area, depending on the trailer's miles towed, weight, size, and the forces acting on the frames. While these steel shapes may exhibit greater resistance to twisting from side thrust forces, they may also have a lower vertical load-bearing capacity than the I-beam shape, which is chosen to achieve a lower weight ratio to vertical load strength. The findings and repair methods discussed in this thread provide valuable insights for all styles of frames.

Part 2 of this post, titled "Inspecting the Suspension Area and Main Frame, " includes images that highlight several failures in the I-beam style frame at the connections of the spring hangers or torsion axles to the main frame, as well as the locations of existing cross supports which can break loose from the frame rails. Please refer to that reply for more information on what to look for regarding the frame. https://www.sunlineclub.com/forums/...e-to-look-picture-heavy-20776.html#post159605

One of the main failure mechanisms in the suspension area of any frame style is excessive metal flexing, which, over time, leads to metal fatigue and ultimately results in cracked metal or welds. When the spring hangers and main frame rails bend too much during turns while towing, the weakest parts of the frame can start to crack due to insufficient reinforcement at the spring hanger area. The more miles that are towed, the more flexing occurs. This flexing can be exacerbated by heavier campers within their load rating, overloading the camper, driving at highway speeds on rough roads, and significant corrosion (rusting) of the metal, along with other factors contributing to frame cracks.

**Camper Frame Evolution.** Keeping this in perspective, Sunline began building campers in 1964, with production ceasing in the fall of 2006. Many club members, including myself, tow campers 22 years old or older, and we genuinely love them. The percentage of Sunlines still on the road today, compared to those with cracked frames, is small in the grand scheme, so don’t assume that all Sunlines have this problem- they don’t. The older, smaller single-axle campers were lighter and experienced very different suspension side thrust conditions when turning compared to double (tandem) axle trailers. As the RV industry evolved, the weight and length of the campers increased, necessitating tandem axles to support the load. During the mid-90s, the RV industry and Sunline began using I-beam-shaped main frame rails. New insights across the industry emerged in the following years when, inevitably, repeated suspension failures started appearing in the field at a low percentage rate. Sadly, history seems to repeat itself with brand-new campers have the same types of cracking from other manufacturers still to this day.

Sunline proactively addressed known weaknesses once they were discovered before going out of business, and we will highlight some of these incremental corrections later in this thread. However, Sunline did not operate long enough to resolve all the issues. If you conduct a present-day internet search for cracked RV frames, you will find numerous reports about new campers with cracked I-beam frames across many brands exhibiting similar web cracks in the I-beam frame rails; this is not a unique issue only to Sunline. I'll pause here to keep the focus of this post on prevention and repair. The sky is not falling, but as our older Sunline campers accumulate towing miles, metal fatigue can lead to cracks. The key is to conduct inspections, and if you discover any issues, develop a plan promptly to repair and reinforce them, then enjoy your camping experience. A skilled welding or trailer shop can perform these repairs effectively if they understand the requirements. If you do not address the problem and leave it uncorrected, it will worsen as the miles add up and may leave you with a significant problem while on the road.

**The Problem:** Before proceeding with repairs, it is essential to understand the root causes of cracking to create a long-lasting repair and reduce recurrence. We will discuss three areas requiring frame reinforcement. Your camper may already have some reinforced or none. If all three areas are not reinforced, cracks may/will continue to develop as the towing miles accumulate.

The RV industry utilizes a slender I-beam shape that likely originated from the manufactured housing sector, known as MH beams. These beams have thin top and bottom flanges, measuring between a nominal 1/8” thick on the Sunline 6” frame and 3/16” thick on the Sunline 10” frame. Both include slightly tapered flanges and a radius between the web section and flanges, indicating that they are solid rolled beams (which is advantageous) and not three-piece welded. This I-shape is designed to provide greater strength than other steel profiles when supporting vertical forces relative to their metal weight, making it appealing for weight savings. However, these thin I-beams possess vulnerable areas when subjected to side loading, thrust, and twisting; therefore, they must be adequately reinforced in the suspension hanger area to handle the stresses of non-steering tandem or triple axles found in RV campers. The top and bottom flanges of the I-beam carry heavy vertical loads, while the web section helps prevent the top and bottom flanges from twisting/buckling and holds a smaller portion of the vertical load. Increased side thrust or twisting loads acting on the slender I-beam shape, including the bottom flange where the spring hanger is attached, must be managed with sufficient reinforcement in the appropriate amount and location.

Since the trailer axles do not steer, the tow vehicle drags the camper across the pavement during turns. As the tires roll and slide, they scuff against the pavement. The sliding friction between the road and the camper tires generates high thrust forces that act on the camper suspension, flexing the spring hangers during towing turns. While it is not practical to alter the friction between the tires and the road, the camper frame and suspension must be sturdy enough to withstand side flexing loads without overstressing the I-beam. It is normal for the metal to flex, and a small amount of flexing is acceptable; however, excessive spring hanger flexing can lead to issues once the I-beam undergoes repeated complete reversal bending beyond its yield strength. Once the bending of the I-beam web section has occurred repeatedly beyond the yield strength, the stress in the metal will surpass the ultimate tensile strength, resulting in cracks. This problem does not arise after just a few turns; it takes many turns to observe damage in the form of cracking.

These cracks can appear in various locations on the web section, but they all stem from the same cause: excessive flexing of all six spring hangers on a tandem axle setup. Often, web cracks may appear in several hanger locations by the time you inspect for them, even if they do not crack all at once.

These three areas of reinforcement are needed to help lower the flexing of the I-beam lower flange:

1. The lower flange of the I-beam is to be reinforced to prevent the spring hanger from excessively flexing the web section. The I-beam's lower flange and web section cannot endure constant excessive flexing back and forth caused by the spring hanger.

2. The spring hanger, welded directly to the bottom flange of the I-beam, must be reinforced to be rigid enough as a unit to prevent side flexing of the U-shaped sides during turns while towing.

3. Cross supports installed between spring hangers must be strong enough to minimize excessive flexing of the hangers.

If you have welds that fail, the excessive flexing will accelerate the deterioration of poor welds, leading to cracks. However, when the weld is executed correctly, it will be stronger than the base metal; the metal will fail while the weld remains intact. If you have failed welds, they must be ground out and redone, and all three reinforcement areas must still be addressed.

The goal is to minimize excessive flexing of the spring hangers during turns, reducing stress and bending of the I-beam’s bottom flange and preventing excessive flexing in the I-beam’s web section that could initiate a crack.

NOTE: Based on my research and personal experiences with towing and repairs, implementing the three reinforcement strategies mentioned above has effectively lowered the hanger flexing, leading to the cracking of the thin I-beam web section. I am not the only one who knows these three needs, as I have learned some of this from other RV manufacturers and individuals. Repairs that include none or only one or two reinforcement areas addressed tend to fail after mild towing mileage. Fixing a stressed and cracked frame can lead to a loss of strength in other areas that may remain undetected during the repair process, potentially resulting in cracks appearing in different locations many years later. Corrosion on the frame or other damages also increases the risk of developing cracks. Remember that there is no 100% guarantee that a repaired or reinforced frame will never crack. The odds are low but not impossible. What is described here reflects the understanding at the time of posting and to help extend the life of your camper.

Introduced in 2005, a 6-inch tall, nominal 1/8-inch top and bottom flanges and web section I-beam frame was utilized in all 5,500 to 7,000 lb. GVWR non-slide class travel trailers up the last 2007 model camper. The first set of images will help us examine the area we will discuss. The camper illustrated is a 2007 T2499, 7,000 lb. GVWR class trailer with leaf spring suspension. This camper received the last batch of frame updates before Sunline ceased operations. This frame is not cracked, partly because it has not been towed much since 2015, when it remained idle and returned home with me in 2019, and is still sitting idle awaiting major water damage restoration. Campers of this frame size on other models have cracked frames, as highlighted earlier in this post. The 5,500 lb. rated campers with the same frame setup have also developed cracks after sufficient towing miles; weight is not the only issue; it could be that heavier campers experience web cracks with lower mileage.

Note: Sunline only used an 8” tall I-beam frame on the 2007 T-195SR, which was required to accommodate the slide drive system. It is in the 5,500 to 6,000# class travel trailer.

These pictures show a 2003 manufactured 10” tall nominal 3/16-inch top and bottom flanges and web section I-beam trailer frame from my 2004 T310SR, a 10,000 lb. GVWR trailer. This frame was used on trailers in the 8,600 to 10,000 lb. GVWR class, which began being used in the mid-90s. We will see later that Sunline began making incremental corrections by adding extra reinforcements to address failures observed across the RV industry with this frame style.

I am presenting my research and findings on restoring older campers to assist fellow campers in keeping their trailers on the road. Please consider this a collection of ideas for reflection rather than strict directives to follow. Other methods may be equally or more effective than those suggested here. If others have ideas to contribute, feel free to post and ask questions about my findings. We can all learn from each other.

Both frame sizes experience the same issue of excessive spring hanger flexing, which, as towing accumulates, leads to cracks in the I-beam. Other factors can influence the cracking, either exacerbating or alleviating the problem. These include the camper's weight, spring hanger length, I-beam size and strength, the location of factory-installed components such as waste or water tanks, and the presence of preinstalled frame cross supports or reinforcements in the hanger area, to name a few. In some instances, these factors are related to the floor plan.

At the equalizer area. The 6” I-beam frame cracked web section on a 7,000 lb. GVWR trailer. (2007 T2499 in this case)

At the front or rear spring hanger. The 6” I-beam frame on a 5,500 lb. GVWR trailer (2005 T1950 in this case)

In summary, a sequence of side forces acting on the suspension occurs when the trailer goes through a turn. This picture diagram was made to show the issues.

Trailer and truck are towing going straight ahead. The leaf springs, spring hangers, lower I-beam flanges, the I-beam web section, and the top I-beam flange all have low side stress acting on them. All is good at this point.

As the trailer goes into a right or left turn: The side thrust forces from the camper turning during towing acts on the leaf springs, spring hangers, lower I-beam flanges, the I-beam web section, and the top I-beam flange all start to rise and have higher stress forces acting on them. The sharper the turn, like a 180-degree U-turn of the camper, the more stress. However, even with many gentler 30-degree turns, the spring hangers absorb all the side thrust forces from the leaf springs. The hanger flexes back and forth, from right turn to left turn, bending/flexing the I beam lower flange in a complete reversal of forces, which flexes the I beam web section. The turning stress forces are expected due to the non-steering axles. The problem begins when the amount of side flexing stress within the hanger gets too high due to excess flexing and how often it occurs. After enough back-and-forth side flexing of the spring hanger, the stress limits of the I-beam web section are beyond the yield and tensile strength limits, and the web section cracks. A simple example is the paper clip you may have played with before. If you repeatedly bend the paper clip back and forth, it will eventually break into two pieces. The weakest component breaks first; in this case, the I-beam web section is usually the weakest area if all the frame welding is done correctly. These thin I-beams cannot withstand constant excessive flexing of the flanges or web section in complete reversal motion.

***The repair and added reinforcement needs.***

NOTICE: Any repairs and the methods used to address the issues with your camper, along with the liabilities and warranties that will resolve your problem, rest solely with the firm or individual performing the repair. The installing shop may use any of this information as it is presented and take full responsibility for its use.

Note: The descriptions below are intended for an experienced welder. If this is your first welding project, here’s a friendly heads-up: this project is not for you currently. Start with a non-critical project to learn. For this project, find a friend who welds for a living or hire a welding shop. There are too many things to know in advance that cannot be conveyed in words. Welding is a skill that takes time to learn and perfect with a mentor or through a training program, and then you need to do enough welding to understand your limitations.

Repair needs:

-If the frame web section is cracked, it must be repaired.

-A close inspection of existing frame cross members and welds must be inspected for failed joints and corrected.

-If the spring hanger welds and side plates show signs of cracking or failure, they must be thoroughly inspected, repaired, or replaced. Also, check the hanger's bend radius closely.

- Conduct a dye penetrant test to check for cracks and if there are doubts about the integrity of a spring hanger weld, hanger metal crack, or I-beam metal crack.

-The web section, the lower I-beam flange, and the hangers need additional reinforcement to reduce the bending stress at the hanger and lower flange connection to create a lasting repair.

Addressing all three areas discussed above under the “Problem” paragraph is essential to minimizing the stress-generating regions and achieving a more durable repair that is better than the original. Remember that restoring the frame to its original state is insufficient, as it was not reinforced enough to start with under normal highway towing.

Repair the web section crack.

This method follows standard fabrication repair for cracks with some additions to the camper’s thin I-beams.

A. Using a standard fabrication stop drill technique, drill the ends of the crack to help prevent the crack from growing after the repair. A 3/16” or 1/4" drilled hole is sufficient. Prick-punch the ends of the crack and ensure you put the point of the drill bit at the end of the crack. This stop-drill approach provides a full radius end section at the end of the crack to help distribute any future stress in this area.

B. Inspect the interior of the frame to identify what is behind it. LP gas lines, wires, heat ducts, and piping may be present in the area, so care should be taken to avoid affecting them during the repair. The objective is to achieve a full penetration weld of the crack. Due to a lack of access, the welder will determine whether this can be executed from both sides or must be done only from one side. Additionally, the welder will assess whether a backing plate is needed for the one-sided full penetration welding.

C. Note 1: These I-beams are made from high-strength, low-carbon steel (HSLC) and have a tensile strength in the 70,000 psi range. To ensure the full strength of the repair, consider these filler metals for welding. If you use stick welding, use an E70XX rod, typically E7014 or E7018. I have used both rods with success. If using MIG, utilize weld wire that meets or exceeds the ER70X-X classification. You can use solid wire, R, for gas shielding or T, for flux core, and the coating you select for mild steel. I use ER70R-6, which can handle some mild mill scale with a 75/25 argon/CO2 gas mix.

D. Note 2: Exercise caution when welding these thin I-beams. Pay close attention to the welding location, duration, and the amount of heat applied during the process. Using short stitches and allowing the metal to cool to the touch before adding additional short welds to pick up where the last weld ended, helps limit heat buildup in place of a single long 3 to 5 inch long continuous weld bead. Move around to other welding areas to keep the work progressing during the cooling phase and return when everything is cooled to add extra stitches or extra weld length. Applying excessive heat below the center of the beam can cause it to bend downward, and the heat shrinkage of the weld can inadvertently warp the frame in the wrong direction (negative camber). Be especially vigilant about the rear hanger area of campers with overhung frames; a negative camber at the rear hanger can lower the back of the camper, resulting in potential issues with entry doors or slide rooms becoming out of square.

E. Disconnect both battery cables (+ & -), shut off the LP at the tank, and purge the gas piping system. Unplug the camper from shore power.

F. A heat shield protects the black plastic membrane from the welding flash fire. I cover the local weld area with a piece of sheet metal and slide it between the frame and plastic membrane to secure it during welding. These pictures are from a frame header repair, but the same sheet metal can also be used in the axle area.

G. Most web cracks require a horizontal weld, though some may be vertical. Position the welder ground clamp on cleaned metal as close to the welding operation as possible. Apply a full penetration weld along the entire length of the I-beam web crack. Remember the heat warping concern, accumulate shorter weld stitches cooled between weld beads to create a full length weld.


Reinforcement Area 1. Reinforce the I-beam web section and lower flange.

I have taken several approaches to this area, depending on whether the frame is already cracked or if reinforcement is added to prevent cracking. All six regions where hangers are attached need a form of web section reinforcement to the lower flange.

After the web crack is welded, choose a method to strengthen the web and lower I-beam flange. The web section has cracked due to excessive hanger flexing of the lower flange of the I-beam.

Vertical rib method. This is the latest method I have used and seen others use, and it has several benefits. Create two 1/4” thick vertical ribs cut and fit between the top and bottom flange that will go only in the hanger zone. The bottom of the rib to fit tight to the bottom flange. Grind smooth flush local spots in the crack weld repair so the rib will fit flush to the web section. These pictures are from a 2007 T-286SR on a 10” I-beam camper with an 8,600 lb. GVWR.

These pictures are from a 2005 T1950 on a 6” I-beam, 5,500 lb GVWR camper as part of a front hanger cracked web section repair after painting.

These pictures are from a 2005 T2363 on a 6” I-beam, 5,500 lb. GVWR camper as part of a reinforcement effort before web cracks start after paint priming.

Welding approach:

H. Apply all welding precautions as detailed in items B through G, as relevant to the section on repairing the web crack above when welding on the I-beam.

I. Tack weld the vertical bars into place. Ensure that the ribs are evenly spaced within the width and length of the hanger. No ribs should extend past the width of the hanger. The ribs above the hanger should directly support the hanger’s flex.

J. Use short, 3/4” to 1” long vertical fillet welds in an alternating side stitch pattern to attach the bars to the web section. Important: Balance all vertical weld lengths above and below the center of the beam. This balance of heat will help prevent the beam from warping upwards or downwards. The weld beads above the centerline tend to curve the beam upward, while those below the centerline tend to curve the beam downward. Balancing the heat minimizes the cambering effect as close to zero as possible.

K. You do not have to weld the top of the ribs to the top flange. It will not hurt the repair if you do, but it may melt the underbelly.

L. Last, add fillet welds to the bottom of the ribs to the bottom flange, both sides of each rib.

Advantages to dual vertical rib approach.
- Strengthens the lower flange to the web section directly at the hanger. The bottom of the ribs helps prevent bending stress from the hanger from flexing the lower flange and web section.
- Allows, in some cases, added reinforcement over the cracked web section.
- Allow all exposed welds and metal to be painted to prevent corrosion in the repair area.
- Adds less heat to the I-beam during the repair than other methods.
- Adds less material weight.
- This method can repair a cracked frame or reinforce an uncracked one.

Other web section repair methods.

Lippert Repair method.
Lippert has released a repair procedure for I-beam web cracks. If you contact customer service, they offer the repair plates for sale. We have uploaded two of their older repair methods, LIP Sheet – 0135 Rev A, each featuring different images. Additionally, a third method, the latest one obtained directly from Lippert as of 3/18/25, is called SF-013. All three methods explain the same general procedure, with SF-013 being the most recent version, dated 12/18/17.

Lippert, Lip sheet 0135 Rev A, Version 1 https://www.sunlineclub.com/forums/downloads.php?do=file&id=5655
Lippert, Lip sheet 0135 Rev A, Version 2 https://www.sunlineclub.com/forums/downloads.php?do=file&id=5656
Lippert SF-013 (latest) https://www.sunlineclub.com/forums/downloads.php?do=file&id=5657

This Lippert method was used on my camping friend’s 2007 Komfort travel trailer

I called Lippert Technical Service on March 18, 2025, to confirm their latest repair method; they sent me an updated copy linked above as SF-013. They were very helpful with technical guidance. A few takeaways:

- Their 10-gauge reinforcement plate is suitable for all campers with I-beam frames. The angle plate may need to be trimmed to fit in the web section of your specific frame. You are getting a generic bent plate of material that will be field-fit as required.

- I specifically asked about the heat generated from welding the angle plate. They want it welded entirely all around. I raised concerns regarding the negative camber potential from all the weld heat in the frame. They replied that if a negative camber is identified after welding, you must re-camber the frame to ensure it is straight.

- They did state that to help minimize the chance of negative camber behind the rear hanger, the back end of the frame rails should be jacked up to unload the frame slightly above the natural resting place so the camper's weight does not act downward, worsening the potential for an adverse camber effect.

Advantages:
- A frame builder created the method; it is field tested.

- Premade reinforcement angle plates from 10 gauge steel are available from Lippert, part number 106124.

Disadvantages:
- The Lippert plate might need to be trimmed to fit a 6-inch frame. However, if you possess a grinder cut-off wheel, plasma cutter, or oxy/acetylene cutting torch, this is not a major concern.

- My most significant concern is the large amount of unbalanced weld heat above and below the center of the I-beam. The vertical welds, which are all below the center of the web, are especially concerning. The procedure calls for 100% all-around welds.

- If you use this method, you must understand how to use heat shrink straightening to re-camber the frame. This is doable but requires prior training to do successfully.

See next reply for the continuation of Part 4, Suspension area repairs.

 

[JohnGB]

Continued - Part 4, Suspension area repairs.

Add longer lower flange reinforcement added "only" to uncracked frames.

This extended lower flange plate method, applied to the front and rear hangers, resembles Sunline's technique used in the equalizer area of the 10-inch frames. However, it is longer, which aids in more effective stress distribution on the web. See here for what Sunline implemented. After many towing miles, this method has still led to cracking in the frame web at the equalizer area; the cracks appear above the plate on the web.

I do not recommend using this method on a cracked frame, but it has proven effective for nearly 50,000 miles of towing on a 10,000 lb. loaded camper when paired with additional hanger support and cross-tube supports. All three areas must be reinforced for this to work effectively. Before I learned about the vertical rib method, I utilized this added plate on two 10-inch I-beam Sunline frames that had not yet cracked, which continues to work well. In conclusion, the vertical rib method offers several advantages over this approach. Both are effective for reinforcement before a crack.

Add a 2 in. wide x 24 in. long x 1/4" thick flat bar spaced central over the hanger.
Stich weld the flat bar to the web and outer edges of the flange. Let each weld cool before adding additional stitches.

Test fit at the rear hanger. Sunline 2004 T-310SR, 10,000 lb. GVWR, 10” frame.

After welding at the front hanger.

Advantages to lengthened plate approach:
- Strengthens the lower flange over a long section of I-beam.
- Reduces concentrated lower flange stress.
- It can help reinforce the lower flange from buckling at the rear hanger when towing over rough roads with an extended rear hanger overhang floor plan.

Disadvantages:
- Only recommended for non cracked I-beam frames.
- You cannot paint behind the support plate, which lowers the corrosion resistance.

Reinforcement area 2, the spring hanger

This reinforcement strengthens the standard 1/4” thick hanger's side legs to reduce side flexing. It works with Reinforcement Area 3, Hanger Cross Frame Supports, to minimize the flexing stress loads on both sides of the hanger and not to overstress the lower I-beam flange. This hanger flexing shows up worse on longer hangers. However, even short hangers can benefit from being reinforced.

The tire size, suspension, camper weight, rack and pinion slide drive, and fender well design require a 5-inch long hanger used on the 10-inch I-beam frame. While Sunline did add cross-frame support near the hangers, before approximately mid-year 2005, they used this 5” hanger setup, which can have too much side flex.

Sunline started adding a 1/4" thick x 2” wide flat bar welded central in between the hanger on the 2006 model year campers with the 10” frame. The equalizer area lower flange reinforcement plate was inside the frame on this model—a picture from a 2006 T264SR.

I have adopted adding the 1/4” plate method on all campers when the cross supports can be welded to the side of the hanger, as shown in the next section, Reinforcement Area 3, Hanger Cross Frame Supports.

As seen here, on a 6” I beam frame in repair, the 1/4" thick plate x 1 1/2” tall is made shorter due to the shorter hangers. To prevent interference with the spring, you should leave at least a 1/4” clearance between the bottom of the reinforcement plate and the leaf spring eye. This picture is from a 2005 T-2363 being reinforced as a proactive measure before frame cracks start.

Sometimes, the welded-in hanger reinforcement plate obstructs a bolted-on cross tube, especially when the cross tube needs to be removed to repair a wastewater tank. In these cases, "sometimes" the plate can be shifted off-center and welded in place to allow your cross-tube bolts to work with the hanger.

There is also an option to use a piece of 2” Sch. 40 pipe between the large 5” hangers when the cross tubes are bolted in place for future waste tank repairs. This is a unique setup where the 2” pipe fits between the hanger, and a 1/2” pipe spacer with 1/2" bolt goes down the center of the 2” pipe spacer. The center 1/2" spacer is added to not crush the frame hanger into the 2” pipe spacer open center as the 1/2” bolt, torqued to 120 ft-lb can deflect the hanger metal into the hollow 2” pipe.

The 1/4” weld-in-plate method is straightforward and not complex to add if it can work in your situation.

Added information on hanger reinforcement
I want to add some information I found about adding a V-shaped flat bar between a spring hanger to increase stiffness. This V bar appears on some new-brand campers and some on the internet sites, declaring it the fix for hanger issues. Everyone has an opinion, and I will add mine.

This is the V bar addition I am referring to; I have seen it now used on some Grand Design travel trailers and other brands.

You can buy the V bar from Lippert as a spare part; they call it: ANG 3.313 X 3.313 X .179 L1.813 SKU #: 10372 and can be bought here. https://www.lippert.com/ang-3313-x-3313-x-179-l1813-103727

I have no objection to adding that reinforcement when the camper is built. It is a good idea. Any weld heat distortion (negative camber) while creating the frame at the frame shop can be overcome by adding a positive camber to the frame as a final step by welders who do this every day with all the right equipment without the camper floor on top. However, that design has been around for a long time, and while it is an incremental improvement to reducing hanger flex, there have still been I-beam frames with web section cracks when installed as OEM in the web section, and no hanger cross supports were added. Here is an example from this post: reply # 3. This is from my camping friend with his 2007 Komfort travel trailer, a 10,000 lb. GVWR trailer with a 10 I-beam frame.

Here is a link to more pictures. Scroll down to see them. https://www.sunlineclub.com/forums/...e-to-look-picture-heavy-20776.html#post159605

I would caution against adding this V bar reinforcement and declaring it a total fix for a cracked web or hangers. During welding in the field after the camper is built, two long weld beads need to go across the full face of the I beam, and there are six hanger locations. Those 12 lower flange weld beads can potentially add a negative camber to the trailer frame. Add weld heat to the other I-beam welding to strengthen the web section; you increase your risk of negative camber being created by so much welding on the I-beam. If you go with the Sunline approach and add the 1/4” thick plate between the hanger, that weld heat has minimal impact on the I-beam camber as it was not direct on the I-beam. Think it through on the total repair process as to the needs. V bars with no cross tubes is not a total fix.

Reinforcement area 3, Cross supports between the main frame.

This last reinforcement has the most significant effect on reducing the hanger flex at its source. All three areas need attention, but this area connects them all. Unfortunately, many campers do not come with this installed as OEM. While Lippert is a subcontractor for the RV industry, they will only install this concept if the RV manufacturers request it. In our case with the Sunlines, it may not have been as widely recognized as it is today that such a positive effect can arise, which might explain why the Sunlines never included it since that ceased option in 2006.

While working on this area, inspect “all” existing cross members between the frame rails for cracks between the cross member and the I-beam web section and repair as needed. The hanger flexing the bottom of the I-beam can also crack loose existing cross members.

Options for hanger cross tube support

MORryde sells aftermarket bolt-on kits for travel trailers and fifth wheels. Yes, the problem is large enough that aftermarket companies are selling fixes for it. They call it the X-factor crossmember. They have a few different styles to work with different equalizers. If you need a drop-down cross member in case it interferes with a tank, etc., they offer a drop-down kit. This is a good start for camper owners who want to help reinforce the frame before it cracks and requires no welding. I have helped a friend install one of these on his large fifth wheel. They are well made and work well.

https://morryde.com/products/x-factor-crossmember/
Their standard kit is here PNM XF-001. ; they offer other add as needed. They have a qualifier sheet that shows it will work with your setup. https://shopmorryde.com/products/x-factor-crossmember

Etrailer markets them as a retailer, but they can also be purchased directly from MORryde and other retailers. https://www.etrailer.com/Accessories-and-Parts/MORryde/MR33WR.html

Creating your own cross-member supports.

You have a few choices regarding how to do this.

The Lippert document SF-013 (https://www.sunlineclub.com/forums/downloads.php?do=file&id=5657) shows how to create the cross support using 2 x 2 square tubing and end plates welded to the hanger. This approach is sound if it fits your situation and you have access to the materials.

Next, you can create your own using Schedule 40 black iron pipe, found at a plumbing supply store or some lumber yards. The pipe needs to be strong enough to not buckle in the center. I will show what I have used and worked successfully.

On the 10” I beam frames, use the nominal size, 2” Schedule 40 black iron pipe for a 10,000 lb. or 8,600 lb. trailer. You can use 1 1/2” Schedule 40 black iron pipe on the 8,600 GVWR campers. For a 6” frame, use the nominal size 1 1/4” Schedule 40 black iron pipe on 5,000 to 6,000 lb. trailers. Remember, on pipe, those sizes are nominal numbers; the OD of the pipe is larger in diameter than the nominal size. See below for both a welded-in and bolted-in option in case you have tanks in the way needing to remove the cross-support to service the tank.

Sunline 2006 T264SR on 10” frame with 8,600 lb. GVWR was added as frame reinforcement before cracking started and welded directly to the hanger.

Sunline 2004 T310SR on 10” frame with 10,000 lb. GVWR with bolt-in option cross tubes for tank access. This camper needed an axle lift for more tire fender clearance, so it has extended and extra-reinforced hangers. However, you can use the bolt-in tube option without all the hanger extension work. Frame reinforcement was added before web cracking started; however, bent spring hangers prompted the reinforcement.

Sunline 2005 T1950 on the 6” frame with a 5,500 lb. GVWR using 1 1/4" sch 40 pipe. Web section was cracked in several places.

Sunline 2005 T2363 on the 6” frame with a 5,500 lb. GVWR using 1 1/4" sch 40 pipe. Reinforcement was added to all hangers before cracking started as a preventive measure, as the owner wants to keep this camper for years and years. The cross tubes were welded directly to the hanger.

This floor plan requires a front hanger cross tube to jog around a drainpipe..

I hope all this helps. Feel free to add to it and ask questions concerning your camper.

John

 

[Sunline Fan]

John, towing aside, are there any specific advantages while in storage to support the trailer from the front of the frame so that the weight is not stored only on the tongue jack long term?

I know we've previously discussed how it's not a great idea to store the trailer with all scissor jacks down in case a tire goes flat (although I store my 286 this way and watch the tire pressures), but I'm wondering if there's advantages to storing with at least the front jacks down.

 

[JohnGB]

John, towing aside, are there any specific advantages while in storage to support the trailer from the front of the frame so that the weight is not stored only on the tongue jack long term?

I know we've previously discussed how it's not a great idea to store the trailer with all scissor jacks down in case a tire goes flat (although I store my 286 this way and watch the tire pressures), but I'm wondering if there's advantages to storing with at least the front jacks down.

Hi Jon,

I'll give you some of my thoughts on your topic as there are a few things to think through.

The BAL scissor stabilizers on the Sunlines are not a true jack per se. They are made for stabilizing when the camper is set up for camping. I know we call these jacks as a nick name, however they not rated to lift the weight of the camper. BAL specially says this in their owners manual. See the support tab for more on this under install and operation. https://balrvproducts.com/product/classic-scissor-jacks/

I have the 7,500# static rated ones, like your on your T286SR. The key being static rating, not a lifting rating which is a dynamic loading. On mine, they unscrew themselves due to the heavier camper if I attempt to lift much weight, they are not bending any under stabilizing, they cannot hold the weight of trying to lift. I do lube the acme screw on them which I'm sure the lowers friction also affects the back off. Your camper is lighter than mine so you may not see that issue, but still they are not made to lift or support the weight of your camper.

The tongue jack is made and rated to lift and support the weight ratings. It is not hurting the jack by sitting all winter or years on end, not moving.

The camper frame is not hurting either when resting in place. Yes, keep the tires aired up, they need that to have long life in storage. If you are trying to help the camper frame during storage with the stabilizers, lets think about that a moment.

Fortunately, we have a Sunline with a 10" main frame in the larger Sunline campers. The camper when stored has plenty of frame strength to handle storage without any extra support. I have high confidence that Sunline frames will not be damaged in storage standing still. Again, assuming you are not overloading the weight inside the camper, which I doubt you are.

In your case, you have extra frame capacity as a safety margin as long as you adhere to the 8,600# max loaded GVWR. After doing all this frame and suspension work and investigating other Sunlines, I discovered your T286SR rated at 8,600# has the same frame, springs, axles, and tires as the 10,000# GVWR Sunlines. I'm not sure why Sunline derated the shorter, larger slide campers. It may be the same reason the smaller 5,500# rated campers have the same axles, tires suspension and frame as the 7,000# GVWR campers in the more newer ones. As they were made, the Sunlines have much more cargo capacity than most new campers still built today.

Point being, the camper frame during storage, is OK, no issues and they do not need help with extra supports if you are trying to help the frame.

Use this analogy: you have a great shape Excursion with a frame with less capacity than your Sunline T286SR does. Do you worry about the Excursion's frame during the off-season? Ah, I didn't think so. Grinned: Don't worry about the Sunline; it's good.

I hope this helps to wrestle with the decision.

John

 

[JohnGB]

For those who subscribe to this post, it turns on the yellow light as something new; I updated the fourth post on the thread today, extra frame areas to inspect on specific years and models.

More yet to come.

 

[JohnGB]

For those following along, I have updated section 4, which talks about how the main frame rails using I-beam frames can crack in the suspension area and how to repair and reinforce them to help prevent future cracking.

See these replies, replies 6 & 7, which have been updated.

Part 1 of the suspension area repair. https://www.sunlineclub.com/forums/...e-to-look-picture-heavy-20776.html#post159608

Part 2 of the suspension repair https://www.sunlineclub.com/forums/...e-to-look-picture-heavy-20776.html#post159618

There is a lot there to explain what causes the problem and how to repair it. Grab a cup of coffee, an easy chair, and some time to read it.

While camping with friends in the summer of 2024, I set a new record; I found four additional campers with frame cracks. Three were Sunlines from the 2000 to 2007 model years, and one was a 2019 Grand Design travel trailer, a 10,000 lb. GVWR-rated camper with the newer 8” tall I-beam frame that showed web cracks at all four spring-end hanger locations. I hope this is not a new trend, as this newer 8” I-beam is now used extensively across the industry on heavy campers.

Now is the time to inspect your camper frames before the camping season starts.

Thanks,

John