I am adding to an older posting, but I wanted to tell a story about axle problems, tire failures, and what I ultimately had to do.
I acquired a used (two prior owners) 2011 Keystone Passport trailer - two axle ~ 30ft (box length). My daughter, husband, and family immediately took it on a trip to Nova Scotia. They had flat tires (blowouts) going and coming back. One of the tires shredded damaging the underpan and fender skirt. They bought new tires and continued on.
We parked the trailer at my place and I observed that the tires were visually out of alignment. I asked Keystone via email about this without a response. My wife and I then took the trailer across country to the National Parks. I noticed that the rear tires canted inward/outward when turning into gas stations. The rear tires were also wearing out on the inside tread with steel cord showing in 3000 miles. Alarmed, I contacted Keystone and they said my trailer had 2.25 inch axles with wide axle spacing and that the rear axle should be upgraded to a 3.00 inch axle (over $500). They provided a spec sheet to be used by their dealers. The axles were made by Dexter. I tried to arrange for this installation in Utah but could not receive the replacement axle in time. While doing some research, I found an axle alignment shop in Salt Lake and had both axles re-shaped/bent to achieve an straight alignment in both camber and toe-in ($160). Both axles were out of spec. I thought the problem was solved, although I wondered why we had the problem to begin with. There was no indication that the trailer had been abused. The last owner even gave us his high-end leveling and sway control hitch.
We continued our travels back to the East and I watched the axles and tires along the way. I also was very careful not to stress the rear axle by making the broadest possible turns in gas stations and other tight places. When we got home, it was visually obvious that the rear wheels were again out of alignment. I wrote Keystone and asked them to help (technically and financially) because it was now obvious that the axles were bending out of alignment during normal use of the trailer and that this condition was unsafe. They called me and asked me to take the trailer to one of their dealers for an inspection. I did this and the dealer made camber and toe-in measurements showing that the alignment had shifted. When they contacted Keystone, Keystone said that they would not assist because the trailer was outside of warranty -- an obvious statement that could have been made without going to the dealer.
My lawyer brother-in-law said that it would be too expense to "go after" Keystone under "merchantability, that is, suitable for its intended purpose" which would not necessarily be a warranty issue -- better to just buy the axles and repair the trailer -- which I did ($450 without labor). (I had assumed that Keystone would fix this situation on a case-by-case basis rather than issue a recall. I was wrong.) I called Dexter Axles and was advised to buy axles through their dealer network due to better pricing. Ultimately, I bought two 3.00 inch bare axles because I didn't trust either axle, blocked the trailer up, dropped the old axles, swapped the brakes, drums, and bearings, and installed the new axles. This took the best part of a day with the help of a friend and a trip to the store. Since then, we have made a trip with the trailer and the axles are well-behaved and track in a straight line. (I did not have the new axles checked for alignment.) The tires are all new because the past damage done to the old new tires. The new tires do not show any wear at all.
I have pulled double axle boat trailers and utility trailers for years and never experience inadequate axles on properly loaded trailers. (I was so concerned about the travel trailer during the cross-country trip that I loaded all of the heavy items into the back of my truck -- even bottled water.) In my opinion, the original Dexter 2.25 dia. round axles were adequately spec'd for weight but not for torque/stiffness/rigidity; the 3.00 inch round Dexter axles are obviously stiffer and resist flexing and deformation in any condition that I have encountered including sharp turns. This is not a "pothole" issue. Axles should remain true long after tire failure.
One last note: My friend and his wife bought a new 2017 Keystone Passport, dual axle, ~26ft (box length) after our joint cross-country trip. (They had a smaller trailer at that time.) This new trailer came with 3.00 dia. round axles -- Dexter, I believe. Do you think Keystone had become aware of this axle problem?