I can adjust the bottom bracket, it works fine. It's just that with 33x16 gearing and, a longer chain (since the existing chain is too short to work with the 17t cog) it doesn't adjust enough to tighten the chain sufficiently. I should point out that the bike has vertical rr. dropouts too. In order to use the 17t cog I would have to install a half link in the chain, I'd rather use a cog that allows me to stick with a traditional chain, even if I have to lengthen by a link or two.