My suggestion is to take it to a tire dealer. At times the seal can be leaking and just a dismount and remount can correct the problem.
Yep! Had that happen on a car once. They had some "rim sealer goop" that they put on the rims. Remounted the tires. End of problem.
But I would suspect valve stems or even a loose valve in the stem that might just need to be tightened or replaced. You would lose all of the air pressure in the tire but you can replace the actual valve without replacing the stem. I had a bad valve on one of my tractor tires; so replacing it fixed the problem. You don't want any weight on the tire if you try this so that you don't lose the rim seal. And of course you would want compressed air available to re-inflate.
2012 F150 FX4 Ecoboost, 2016 Surveyor 274BHS
2003 Yamaha FJR1300, Demco Premiere Slider
1969 John Deere 1020, 1940 Ford 9N, 1948 Ford 8N
Jonsered 535, Can of WD-40, Duct Tape
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We had a split in the side of on of ours, PT took care of it no problem. There may be a problem on the back side you cant see. Blown tires while towing cause a lot of damage to the trailer so be sure to have it checked out thoroughly. My first big purchase is to replace the factory installed tires.
We had a similar problem with our tires. We had bad valves replacing the stems didn't work. The trailer was less than a week old so we took it to the dealer and they replaced the valves under warranty. So far all is well.
You can diagnosis the tire your self, get a spray bottle and fill it with 5% dish soap and 95% water, spray the entire tire and wait for bubbles. A slow leak will have very fine bubbles almost like shaving cream. If it appears on the side wall or thread with no apparent damage then your tire is not repairable. If however there's a leak around the stem or rim then the tire may be repairable. Bead sealer and a new stem should take care of it.
If they are Chinese tires, I would replace them. It simply isn't worth the risk of having a tire failure.
We replaced ours with Maxxis tires, and upgraded to a higher load rating while we were at it. The Chinese junk the factory put on were minimal at best.
It may seem expensive, but the alternative is far worse.
Hate to break this to you but those Maxxis tires you strapped on are not made here . By no means am I saying it's not better quality than some of the true no frills Chinese slave labor units out there.
Before upgrading to my 16" tires, my tires would not maintain pressure over time, especially while parked.
I installed steel valve stems which seemed to have corrected the problem.
While the tires were off, I also balanced them. I know it doesn't effect the air leakage, but they roll much smoother.