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Might be daft but can I change an internal hub for a derailleur option. I have an old bike which is slow but I do love it. I want to upgrade my running gear but the "chassis" is still tip-top. I don't want to loose my beloved but am sick of the three speed granddad option. I'm aware that this might not be possible but any help you chaps can offer would be great.

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Can you add some photos so we can see if you derailleur hangers and vertical/horizontal dropouts? Mostly photos around the rear axle would be really helpful. –  Mac Sep 2 '13 at 2:00
    
What you're talking about is called hybrid gearing (using a derailleur/freewheel on an internal gear hub.) Here is some relevant writing on the matter: sheldonbrown.com/org/otb.html –  WTHarper Sep 2 '13 at 3:50
    
At least, that is what I think you're angling at. –  WTHarper Sep 2 '13 at 3:51
    
I read it as just wanting to swap the hub gear for a derailleur, not add a derailleur while keeping the hub gear as well. –  armb Sep 3 '13 at 12:11
    
(Sheldon has more on hybrid gearing at sheldonbrown.com/internal-gears.html#hybrid) –  armb Sep 3 '13 at 12:30
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4 Answers 4

Most three speed internal hub wheels are physically very different in configuration from derailleur (external gear changer) style wheels. Internal hub wheels are fairly symmetrical side to side, but on wheels used on derailleur equipped bikes, the spokes are nearly flat on the gear side and dished on the opposite side.

To add a rear derailleur, you would need a complete new rear wheel. There is also the issue of a hanger for the derailleur. Most bikes with internal hubs do not have one. It may be possible to braze one on, but that is complicated.

Adding multiple chainrings in the front is a problem because you still need a chain tensioning mechanism, which is usually done by the rear derailleur mechanism.

Sometimes three speed hubs are added to bikes that are designed for derailleur systems (to multiply the number of gears) but rarely the other way around.

Consider saving the old trustworthy for leisurely rides and investing in a new multispeed bike for more intense activities.

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The vast majority of cheap derailleur bikes from yesteryear used a separate derailer hanger, vs something welded to the frame. The bigger issue is how the dropouts are aligned. –  Daniel R Hicks Sep 3 '13 at 15:03
    
It's an old hub-geared bike. What are the chances that the dropouts aren't more or less horizontal? –  armb Sep 5 '13 at 9:23
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Rather than braze on a mount for a derailleur hanger if you don't have one, you could (almost certainly) use an adaptor claw like these:

(I'm assuming you have horizontal dropouts, since it's an old three speed bike.)

Another option would be to upgrade the hub gears to new hub gears with smaller steps between gears and a wider range than the existing 3 speed, like a Shimano Nexus or Alfine 8 speed or Alfine 11 speed, or even the Rohloff 14 speed. http://sheldonbrown.com/internal-gears.html

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Still thinking about it? Here's one I did last year, rides like a dream, You will probably need a new (threaded) driver for your SA three speed hub. Available from OldBikeTrader for £15, or from any pre 1951 SA hub. To go with that you want a basic derailleur rear mech and changer(5 speed ideal), pennies from e-bay. You might have to switch to a longer (6 1/4 inch) axle for your hub.

Stripping and reassembling SA hubs is not hard as long as you are careful and organised. Excellent video guides on youtube.

Photos of finished article here:

http://www.flickr.com/photos/31231726@N03/8554241017/

http://www.flickr.com/photos/31231726@N03/8554243339/

Youtube stripdown guide here:

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If you have a local bike coop, they're likely to have pretty much all of what you need very cheaply:

  • bolt-on derailluer hangers, as used on old Schwinns
  • a freewheel wheel in the appropriate size
  • basic friction shifter
  • rock-solid old friction derailleur, e.g. Suntour Vx
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