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I have an old Hercules frame that I have no use for but don't want to get rid of - I am in need of a new "town" bike for running around on, however I need something practical with a nice gear range... I like projects and building things, so the thought of building up my old hercules into a useable everyday bike has crossed my mind :) But... is it possible ?

I thought a Nexus or even Alfine speed hub would be perfect, however there would be a 135mm hub spacing required from such hubs, of which my frame is a lot smaller. Its a steel frame so I think I should be abled to modify / cold set the frame and increase the spacing to support a 135mm hub ... ?

Is there anything else that I should take into consideration ? should I worry about the bottom bracket and crack spacing ? can I also upgrade the bottom bracket and crank to something more modern on such an old frame ?

Thanks !!!!

Jon

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    What is the current rear hub spacing?
    – mikes
    Commented Dec 20, 2016 at 11:23
  • Another thing to worry about, besides the spacing, is the axle diameter. Probably it's not a problem, as you generally only see oversized axles on fixed gear bikes, and I assume that the proposed new hubs have "standard" axle diameters, but it's something that should be checked. A mismatch wouldn't be a killer (especially if going from large to small), but it would be another reason for less than optimal operation.
    – Daniel R Hicks
    Commented Dec 21, 2016 at 1:16

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While you probably could cold set it, the Sturmey-Archer XRF-8 is available in a version with 120mm OLN dimension.

(And you almost certainly can fit a modern bottom bracket. Worst case, have the existing threads removed and fit a threadless bracket. Bottom bracket size guide.)

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Aside from the rear spacing needing to be roughly consistent (you can probably fit a wider hub into a frame with a margin of around 10mm without much ill-effect) you'll need to worry about the chainline, which is the correct alignment of the rear sprocket on your Alfine or Nexus hub and the chainring (possibly what you're referring to as the crank – or crack – spacing).

Never heard of Hercules bikes, but if it were a multispeed bike with 2 chainrings, then you have some wiggle room. I've converted a few 10-speeds to singles and fixies and have usually been able to find a combination of crank, bottom bracket and spindle size to provide a chainline within an acceptable range. You also have both the inside and the outside of the crank bolt holes to work with. Again, not knowing what a Hercules is, you may have to replace the crankset (if it's a one-piece BMX crank or a cottered crank then you'll definitely need to replace it).

The expensive (or, if you're up for the challenge, difficult) part of this is going to be building the wheel around the hub, unless you can find a pre-built wheel with an Alfine/Nexus hub in the right wheelsize and rear spacing.

Here's a guide on frame spacing that will come in handy: http://www.sheldonbrown.com/frame-spacing.html

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  • Thanks for the reply and advice !!! The frame is old and only had a narrow 3 speed hub - so the spacing required would be quite considerable... i think 20mm ! re the chainline, yes this was my concern and was womdering if I could fit a wider bottom bracket or front sprocket spacing to make up for the difference ?
    – Jon Williams
    Commented Dec 21, 2016 at 13:14
  • PS this is the (same) frame: tarkaletabikes.bg/wp-content/uploads/2015/03/IMGP4677.jpg
    – Jon Williams
    Commented Dec 21, 2016 at 13:15

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