Bicycle Mechanics - Realigning seat and chain stays
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I have a ten year old (steel) Gemini Randoneur with a 7 speed rear cluster, which I want to replace with a nine speed. The problem is that the axle is too narrow. I do not think that I can get a less dished rear wheel to provide extra room, so I am contemplating getting a bike builder to realign the seat and chain stays so as to provide more room for the wheel and cluster. Has anyone done this before and/or is it possible, and is there any risk with such a procedure?
Spreading the rear triangle to upgrade the rear cogs is common. You could probably get it done by any good bike shop. You could also do it yourself. Search www.sheldonbrown.com for instructions. It's very doable on a steel frame.
There's the more specific link. I've done this a couple of times and it can be a little scarey when you have to put a lot of weight on the jig to bend each side. It doesn't just bend easily and stay there. You have to over flex it and measure how far it actually returns. Sheldon shows a string technique for measuring. I used a graphite golf shaft held against the head tube and seat tube and measured its intercepting of a bolt through the rear drops. You'll probably be over and under bending in a few iterations before you get it perfect. Don't try this with anything but steel frames.
And if the old spacing is 126mm, and the target is 130mm, I'm not sure it's worth it. You can just spread the drops a little bit whenever you need to install the wheel. It's a minor hassle that you'll probably not have to endure very often.
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