I have a Trek Rumblefish one and recently someone pointed out that my rear wheel was a bit wobbly. I also noticed that I heard the disk brake occassionally. I pulled off the rear wheel and was really surprised when my Cassette just fell off. The bolt that holds it in completely came undone. I was also surprised that this cassette design looks like nothing that I am used to as the lockring is not involved with holding the cassette on the wheel at all. So.. Does this happen to a lot of people? How do I properly screw it down? The bolt is reverse threaded and all I could do was hand tighten it, because the axle would begin to spin when I started to screw it in. I was later thinking that a chain whip would do the trick, but didn't try that (This is something also odd to me, usually you use the chain whip to get if off, not put it on). Is there a proper torgue value for this? Did anyone else have this problem?