It's not that they're unsuitable, it's just that the axles tend to get less reliable the larger the spacing is for a freewheel'd bike.

http://pardo.net/bike/pic/fail-025/w...parison-en.jpg

http://pardo.net/bike/pic/fail-025/000.html

Thanks for the link, interesting historical detail.

So if i understood correctly, it is the amount of "overhang" that makes the design inherently weaker when using 6 speed clusters (at 126mm spacing).

So by re-spacing the the hub towards the center of the axle, you decrease the amount of overhang on the gear cluster side. This brings that bearing closer to the frame and should actually reduce the propensity to break the axle.

In other words, if you din't break axles on the bike in the stock configuration (ie with the six speed gear cluster) you would be less likely to do so by converting it to a single speed if you re-spaced the hub.

Is this correct?

I believe he was saying you are likely to have problems with any 126mm spaced rear end compared to a 120mm spaced rear. Maybe I am wrong, dunno. I do know I've ran plenty of 6/7 speed freewheels on my roadies, and as cross bikes as well and not had a problem bending axles. I have bent axles with 7 speed rearends in older mountain bikes, like I pretty much couldn't keep a straight axle in it, whatever spacing they may be. But those took much, much more abuse than my mountain and cross bikes.

Got the bike together last night and gave it a whirl for a handful of miles today after mountain biking. Quite a bit of fun, and boy as a roadie I didn't realize all the times you stop pedalling or simply slow down for such things as looking behind you, obviously slowing, but even just coming to a stop is really weird too. Can't wait to put some more miles on it soon :) Unfortunate it's cold and windy season, but it'll get a bit of use and then alot come spring. Thanks for the ideas and tips everybody!