tire pressure for sure. Happened to me. I was running 205/45 Kumho's on a 8.5" wide wheel and tire the dismounted itself mid corner (i wasn't drifting
) and I noticed a nasty nail in it.
Even if its not properly seated it won't hold air at all.
Ivan, you can stretch anything lol. I had a buddy stretch 225 Rt 615's on a 10.5" rim.