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.

ok, this will answer none of your questions:

48X15 is too tall for you. i'm running that right now at work and paying the price (esp. cuz it's so windy past coupla days). if you need one to try it out, i've got an extra 15 toother in my fixie tool box. i can meet you tomorrow after work or something.

glad i could be of no help.

oh god no! not 48x15! 46x15

oops, my bad.

offer still stands for loaning the 15.

You have to work on cadence to build up strength so spinning can be an asset. You should ride what you feel comfortable and not listen to messengers on mountain bikes.

1) IRO hubs are fixed/free. The difference is that the fixed side has a counter threaded portion for a lock ring. The lock ring is the thing preventing it all from flying apart when you skid/back pedal. Free sides have a large section of threads all in the same direction to take a variety of freewheels and don't take lock rings; unless you like suicide hubs with loctited bottom bracket rings but its really for peeps trying to take themselves out of the gene pool IMHO.

2) I run an 18 on the street and 15 on the track and have no problems. The 15 leaves my wheel very near the end of the dropouts. Someone had a formula for working out distance moved for each drop in cog teeth count. Should turn up via the magic search button.

3) Don't know. But EAI cogs are the buisness and well worth the money.

sweet. do you have the tools for doing the swap? pardon my naievete. what are the tools for doing the swap?

I'm mashing on 46x14 and it's killing me. Msngr can attest to that, but i'm also out of shape. but going from an 18 to 15 can be quite a change, maybe to a 16 or something. I'm gonna switch mine to a 46x16 so i can spin more. Nothing wrong with a bit of spining.

If both sides have threading for a lockring then your fixed/fixed. Fixed/free would mean the other side is suitable for a freewheel.

Ignoring any change in vertical chain angle from ring to cog, a change of 1 tooth will move the axle roughly 1/(2*pi) inches: ~5/32" or 4mm