Can I...?
 

Can I use a 5-speed freewheel on a 126 spaced hub? Or must I use a 6/7 speed freewheel on a 126 hub?

As long as you have a properly adjusted rear derailleur you should not encounter any problems.

Someone had done just that on a bike and posted about it not long ago. He was having shifting issues due to the increased spacing between the first cog and the dropout. I think he solved the issue with a freewheel spacer.

yep, spacer will make it work

I am using a 5speed freewheel on my 126mm spaced Raleigh without any issues. I didn't have to use a spacer to make it work either.

I'm running a 5-speed freewheel on a 126mm hub that I can swap between 120 and 126mm dropouts with only minor limit adjustments to the rear mech and have no problems at all.

+1
But may I ask, why 5? Why not 6/7 aside from lack of funds/parts.
-Gene-

period correct?

Because he has a wheelset with a 5 speed and the Gios I'm sending him has 126 mm spacing?

Well...

Period correctness, mostly.

The Gios (heehee) has 126 spacing, (spread there, we believe?) and I've got a 126 Record hub, and even a 7-speed freewheel, a Shimano Santé, but the 7-speed looks really clunky to my eye, and the corncob Regina Oro looks pretty damn sweet. Small and light and teeny-weeny-racey!

Dunno. Just a thought.

-Nick

The only case wherein I would be reluctant to have the large gap between dropout and small cog would be with an NR or SR derailer. The offset low-stop compensation (for getting around the NR/SR's overshifting problem into the last cog) would render the chances of dropping the chain in the gap too high.

-Kurt

Oh. Well, it was going to be a NR derailleur. :(

Admittedly, I was not familiar with any of the problems of overshifting on these DR's.

(and on a completely seperate note)

In better news, the UCI is going to start pushing back towards "normaller" bikes, as opposed to the really exotic stuff! :D

I haven't seen this problem - yes, there is overshift, but I've never seen it this bad. I really don't think the dropout inner face is part of a chain-jam prevention system.

I'd start with the NR. If it won't adjust right on the stand or a gentle test ride, there may be a problem, but you can reduce overshift by moving the wheel forward or backward in the chainstay. You want to shorten the free length of chain between the cog and the jockey wheel.