What would cause a trailer tire to do this?

Then i do think you hit something.
There is a dark area on the rubber.
That can come from running it flat or hitting something(rubbing it to be exact)

You can have a tire that builds up air between the inner and outer wall and cause damage like this but then it would leak air all the time.

 

Very old tire casing?

 

I bounce curbs and rub them all the time being i deliver in neighborhoods and such. and never has one of my tires done this. i did have a brand new recap on tractor do this a day after put on and shop said there was bad batch of recaps they got . there were several others pilled up there waiting to go back. So maybe bad tire. oh yea and my loads are always right at or over 80,000 lbs..

 

You're on,

 

Manufacturer defect... highway debri...

 

Make sure to get it on camera.

[video=youtube_share;enRKvjKr7l0]http://youtu.be/enRKvjKr7l0[/video]

 

Im takin bets!

 

Notice the dangling forearm and large streak of blood on the ground where he picks his right arm up off the ground...

 

Indeed! Never underestimate the power of PSI!