Heath, I was just thinking, even if those two bolts did come loose, the wheel cant move any further back, as it's under tension, and wont go forwards as the grub screw is pushing against the dropouts. Obviously it would start to dent the dropout over time, but I would have thought you'd hear, and most definitely feel, that those bolts were loose. Plus there are 2 on each side, what're the chances of it happening?