I recently converted a 1980ish Fuji Espree into a fixie. It was a lot of fun to do, and a nice way to find out if fixed gear is the thing for me. well, it is and now that i'm trying to fine tune it all, i'm looking for advice on how to take it up a notch. i've got 126 rear spacing, and i've done my best to respace an IRO flip flop 120 hub. i don't ditch my chain, but my chainline isn't 100% straight. i'm going to try to get it a little straighter by moving the front chainring in, but for a more thorough fix, i'm debating either investing in a 126mm track hub (maybe either the ENO eccentric hub, or a Phil Wood...does anyone else make a 126?), or saving up much longer for a new frame with track ends and 120 spacing. any suggestions?

IRO makes a 126 hub.

I am doing an early 80s Fuji conversion right now I measured the gap in the back and thought it was 120MM.

Did you replace the bottom bracket? I am pretty sure it is english but I am not sure what length axle to buy. Also do you remember the diameter for the seatpost. The one I have is from an old Cannondale and doesn't fit.

I emailed IRO, and they told me all the track hubs have the same 42mm chainline. Spacing is achieved with spacers. You need a new BB to get the chainline right with that hub.

Will

I've switched most of my fixies (six, so far) over to tubulars.

I do not see why you cannot run a 120 hub in a 126 frame if it is chromo. I do. Not a fixie but an AW. I reach through the spokes with my left hand and squeeze the stays together when mounting the wheel and feed the axle into the dropouts with my right.
You could upgrade to a real track hub that way. I plan to on another project of mine.

I haven't replaced the BB. So far I'm very happy with my conversion. I've been riding it every day (with a 120 hub in my 126 frame). Now that I'm sure I want to stick with fixed gear riding, I'm trying to decide the best way to upgrade the whole rig for the long term and simultaneously work out a few of the kinks such as a friction which I believe is caused by a slightly off chainline. At the moment I'm debating between getting a properly spaced 126 hub (and a new BB?), or saving up for a new frame with 120mm track ends to accomadate my existing hub et al (i guess i may still need a new BB). I was looking at maybe the IRO Mark V (other suggestions in same rough price range?). The advantage of just getting a new hub is that it would obviously be cheaper and i DO really like my Fuji frame, but getting a dedicated fixie frame may be a better long term strategy.

You don't get it. You can just space you your current 120mm hub/wheel to fit it in your 126mm frame, You don't need to buy a new frame or wheel. You don't need a new frame or bb, unless your bb stops working, or your frame breaks. Space out your current 120mm hub and wheel. Have a bike shop do it for you, since it seems that you are confused. It is a quick job, probably under $10, way cheaper than a new bb, wheel, hub, frame, etc.

Adding spacers to the hub won't change the chainline. It'll make it fit properly in the rear triangle but the chainline remains the same. The cog and chainring don't move relative to one another unless you add more spacers to one side than the other. That can give you a better chainline but now your wheel's not centered.

You can, however, move your ring on your spider (inside to out or outside to in if that gives you a better line), put thin spacers between the spider and the ring (I believe Harris carries these, others surely do as well), or put thin spacers between the cog and hub (don't have a source but I'm sure some hunting will turn one up). All these will let you change your chainline without buying a new frame or BB. Also, since that's an early 80's bike it's got a cup and cone bottom bracket. You could probably get a shorter BB axle and solve all your problems cleanly.

Or maybe you want to, in which case just do. Don't lie to yourself about why.

thank you bostontrevor, i will try to respace it by moving the chainring to the inside of the spider. If I wanted to perfect the chainline "cleanly" by getting a new BB axle, how would i determine what is the appropriate size? I'm not opposed to replacing some of these old parts, both for the sake of improving the bike and because I am really enjoying doing as much of the work myself as possible as a way to learn some bike mechanics.

You really need to be able to measure the chainline to know what BB you need. If you have calipers, it make it very easy. Measure the diameter of the seattube and divide by half. Then measure from the side of the seattube to the centerline of the chainring and add that to the first number. For example, my seattube is 29mm/2 = 14.5 + 26mm (the distance from the seattube to the chainring centerline is) = 41.5-42mm chainline on the cranks. If yours adds up to 46mm and your hub chainline is 42mm and you have a 115mm BB spindle, you'll need a 107mm BB (8mm shorter spindle will shorten each side 4mm. Was that comprehensible?