Originally Posted by shants

The problem, right now, with the disc bolt on system is that there is really no one manufacturing cogs (is boone still making them), the chainline (not that level's is perfect) situation can be iffy, and there aren't standard flip-flop options. if you're using a front hub, you're going to need to respace, and if you are using a rear, you're most likely dealing with mountain bike hub spacing and will have a freehub body hanging around. the freehub situation is fairly gnarly, because the wheel still has to be dished to the freehub side and the forces generated by the added disc cog are going to be on the under tensioned side of the wheel that isn't built to handle them.