I've been meaning to upgrade my ratio (46x18 !!!) for a while now, but this clincher came this morning when a messenger on a mountain bike made fun of me for it. ("46x18?!?! That's too much friggin' spin!")

I'm thinking of getting a 15-toother to stick on the other side of my IRO hub. I think the ratio will be about right. If I'm not ready for it, I'm not ready for it. I'll work up to it. Plus, 15 skid spots! (Right?)

So here's a three-part question:

1) Is my IRO hub fixed-fixed, or fixed-free. Corollary: what the hell is the difference anyway?

2) I've got 7 milimeters left in my dropouts behind the nuts. Will I be able to use the same chain I'm using now? If not, will there be a way to get a chain that will work for both cogs? (I've only got 3 milimeters in front of the nuts.)

3) Who should I get the stuff from? (New Yawk City y'all) What brands are good for cogs and lockrings? Also, do I need it installed (i.e. I own no tools) or can I do it myself? I don't want to spend much money, but I'm willing to pay for durability. Bikeworks? Trackstar? Should I schlep all the way out to Staten Island and get Tony's help?

Thanks everybody.