This tire came off the rear axle of my friends 5th wheel. Goodyear G rated. I know he was probably running a bit under inflated as all of the 4 tires showed edge wear. They were not balanced and had been on the trailer some 5 years. None of the others showed any wear other than on the edges. He said the breaks hadn't locked up. This is the only wear spot on this tire. Trailer sits level so that isn't an issue.

Would need more information on the situation when the tire came off. Was he turning or going straight? What speed was he going?

Tires on a trailer take a pretty good beating when turning. If they were a little under inflated, they could have broke the seal and easily come off.

It didn't come off. We were wondering about the strange wear pattern. He just replaced all 5 tires on his trailer. Latest guess from one of my friends is cord separation on the inside of the tire.

I would say bad springs and possible lock ups when using the brakes.

If they had been on for 5 years that is toward the end range of trailer tires. Since they sit more that they turn the rubber really starts to break down, between uv rays and the chemical compound not spreading around when they turn. I had a tire blow out with 4 years, the tires still looked pretty new. No bad wear spots, over 3/4 of the tread left, no signs of any foreign object. Just one of those unfortunate things with trailers. Gets kinda expensive.

Looks like someone was playing with a carving knife . . . .

Ive seen many semi trailer tires look just like that, Im sure its a combo of pressure not right and turning and backing, jackknifing trailers when your backing has to be hard on them.