Geared setup for 126mm rear spacing

I'm looking to put some gears on my (currently fixed) bike. The frame has 126mm spacing.

My questions are: what sort of gears will I be looking at? 7spd? Cassette or freewheel? Will I be able to use ergos/STIs or am I stuck with DT shifters?

I'm also tempted to try and stick a 130 hub in there to make things simpler. The frame is 731os which I think is heat treated (although I haven't been able to find out much about this tubeset). Is it OK to spring the dropouts apart and jam a larger hub in there, or will that weaken the heat treated steel?

DO NOT attempt to change the spacing. The rear stays in a 731 tubeset are heat treated 753 and cannot be cold-set without weakening or breaking them.

(the main tubes are 631 and the forks are 531, by the way)

I think you may be able to fit a 6 speed screw-on block in 126 spacing, but a 7 speed probably needs 130. You could perhaps put a triple on the front if you need more than 12 gears. Maybe forget about the rear mech and use the new 11 speed Alfine hub gears?

Cheers, I had a feeling that was the case. Going to investigate the deraileur option though as the alfine is waaay out of my price range. Thanks for the info on 731 btw.

6-speed regular spacing or 7-speed "Ultra" screw on blocks fit 126mm. Also 6-speed cassette hubs. Both will be old, hard to find spares for, and will change poorly compared with modern kit. There might be an STI hack to get 6/7-speed to work, but it will always be a hack, not an optimal solution.

You won't want to cold set it, but it's easy enough to jam a 130mm hub into a 126mm frame, and that's what I'd do in your position. You then have a free choice of all the current and recent 10-speed kit

Shimano made some 7 speed sti in RSX or Sora I believe. Quite hard to come by though.

I think that would be 7-speed "normal" spacing on 130mm freehubs, not the "narrow" spacing of 7-sp screw on blocks for 126mm hubs.

As ever, Sheldon is your friend
http://www.sheldonbrown.com/k7.html
http://www.sheldonbrown.com/freewheels.html

Thanks for all the info.

DO NOT attempt to change the spacing. The rear stays in a 731 tubeset are heat treated 753 and cannot be cold-set without weakening or breaking them.

You won't want to cold set it, but it's easy enough to jam a 130mm hub into a 126mm frame, and that's what I'd do in your position.

I wasn't planning on going for the cold-set option, just pulling the dropouts a couple of mm apart to fit a modern wheel in (i.e. so that when I remove the wheel the dropouts return to their resting position), as mdcctester suggests. Think that's what I'll do if it won't affect the integrity of the steel, as it sounds like the price you pay for STIs.

I think that would be 7-speed "normal" spacing on 130mm freehubs, not the "narrow" spacing of 7-sp screw on blocks for 126mm hubs.

As ever, Sheldon is your friend
http://www.sheldonbrown.com/k7.html
http://www.sheldonbrown.com/freewheels.html

Didn't read Sheldon but no it is definitely for standard 126mm hubs I don't think 130mm 8+ speed hubs will accept a 7 speed block without an extra spacer.