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Simple as that. I thought I could He-Man the fork to fit the hub as it's only 3 mm on either side. Looks like it requires a bit of force and I'm concerned about breaking something in the long-run; either the frame or the hub.

I have a Origin8/Formula front hub and an old steel frame (1970s or so) that seems to be in decent condition.

Which option is best: reduce the hub spacing to 94 mm or widen the fork to 100 mm? And in either case, what's the way to go about it?

The front hub is the top one in the picture below.

Origin8 / Formula track hubs

EDIT
Turns out my problem wasn't spreading the fork. It was the fact that the axle diameter was too large for the fork dropouts. I filed the trailing edge of the dropouts and tried again to spread the fork to accommodate the hub. It fit without issue. Pictures below.

Axle in dropout after filing

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Either, or a little bit of both. First make sure there are no spacers on the hub that can be removed. (Don't try to leave off the locknuts, but if they're thick they can be replaced with thinner ones.) –  Daniel R Hicks Mar 29 '12 at 1:02
    
@DanielRHicks Just added a photo. Looks like theres a 0.5 mm spacer in between the locknut and the cone. The locknut alone is 4.5 mm thick. Where can I get thinner locknuts? Not coming up in a Google search. –  fideli Mar 29 '12 at 5:46
    
Go to a bike shop and ask them to rummage through their odd parts bin. Get something off an old axle -- just try to find nuts with teeth like the existing has. And replace the "spacer" with the thinnest "shim washer" you can find at a hardware store. Your last resort would be to grind down the faces of the cone nuts (and then re-cut the notches for the cone wrench). –  Daniel R Hicks Mar 29 '12 at 10:56
    
Of course, the other option is to spread the fork. It should be able to spread that much, but you need some force from a jury-rigged tool. –  Daniel R Hicks Mar 29 '12 at 10:58
    
Looks like there will be another converted fixie around... ;oP –  heltonbiker Mar 29 '12 at 13:14

2 Answers 2

Three milimeters each side for a large-wheel fork is perfectly inside what you can correct with "cold setting" the fork, without compromising safety. Of course a 70's fork is steel, so better yet, because steel is a good material to do this.

What I would do is to find a good "instrument" to use as a lever. If you get lots of cardboard (or have access to a lawn) you can step over the headtube of the bike with one foot, and over the fork leg that stayed against the ground. Then, with the magical lever, you bend the upper fork leg slightly.

It is important that the lever be rigid, otherwise you will store elastic potential energy in the lever, and so you cannot control so well the 3mm needed on each side.

A rough ilustration is below (fork in black, ellipses are your feet, and lever in brown - suggested a wooden framework):

enter image description here

And most important: go very slowly and check each movement. It is much more tedious to do so, but the result is much better and you avoid regret later (telling from experience). Using a symmetrically dished front wheel (perhaps the very one you will get assembled with the hub) would be best.

Hope this helps.

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Thanks. Curious, how does this method ensure symmetrical dropout expansion? –  fideli Mar 29 '12 at 16:08
    
@fideli the method itself does not ensure symmetry, the operator must do it himself, checking every "move" with a properly dished front wheel, or a ruler, before proceeding to the next. –  heltonbiker Mar 29 '12 at 16:35

Sorry to provide ANOTHER answer, but I think this one might be interesting:

  1. Take a rear (135mm) axle;
  2. Insert two nuts, one around each side, untill they are less than 80mm apart. One of them might be inserted just enough to allow a small piece of thread to show up in the tip;
  3. Fit the axle into the fork dropouts with the bike upside down, so that both nuts are beween the dropouts;
  4. Start to "unscrew" one of the nuts, thus forcing the fork legs to get away from each other;
  5. Unscrew it after a while and check the distance. It might take some time to figure out how much elastic deformation (preload distance) you'll have to overcome before actually making the new distance permanent.

This method is much more controlled than the lever one detailed previously, but it most probably will take much more time (although I think a rear axle and some nuts are easier to prepare than a large improvised lever system).

Hope this helps

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Except, with that fork, I'd rather see the spreading force applied farther up, not near the dropouts, given how the tubing tapers. –  Daniel R Hicks Mar 29 '12 at 19:09
    
@DanielRHicks it makes a lot of sense. Perhaps to spare the thinner ends of the fork and apply the forces, via the threaded method described (wood plates with holes?), a bit more towards the middle of the fork legs. –  heltonbiker Mar 29 '12 at 20:30
    
Yep, a couple of pieces of stout (eg oak) 3/4" stock with two holes drilled in each. Then get two pieces of all-thread rod and nuts and washers. Cut some notches in the wood or use some rubber from old inner tubes to keep the fork from sliding. A little tedious wrenching them apart, but well-controlled. –  Daniel R Hicks Mar 29 '12 at 23:41
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(Or just make two wedges from 2x6 and drive them in from both sides.) –  Daniel R Hicks Mar 29 '12 at 23:42

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