chainline frustration
 

i put together a fixed gear.

frame is an old schwinn le tour with the dropouts spaced at 126mm. rear hub is a dura ace low flange with a dura ace cog. the cranks i'm using are sugino xd's, a tange 103mm bb with the chainring on the outside (closer to the crankarm). my chainline seems to be quite off, causing lots of noise, etc.

whenever i put the chainring on the inside it moves too far, causing the chainline to be off even more but in the opposite direction.

i attemped to measure the chainline of the hub and got ~40mm. sheldon brown's site claims the hub are 35mm?

should i get a larger bottom bracket and then put the chainring on the inside? how can i determine what size to get? could the fact that i have to squeeze my dropouts in order to get the rear wheel in have an effect on my chainline?

i'm sure lots of this has been addressed before but i can't find anything specific to the hubs/dropout spacing problem. i'm mainly asking so i won't make the same mistake i made the first time with bottom bracket length.

Maybe Sheldon's website is listing the 110mm DA hub? Just a guess, and probably a wrong one.

Measure the chainline you get with the chainring on the inside, take the difference between that and what you measured on the hub, double it, add that to 103. This is the size bottom bracket you'd need. For instance, if you measure 37mm on the inside, you'd need ((40-37) * 2 + 103) = 109.

I'm guessing 109 is what you'll end up with as the XD's are supposed to give a 42mm chainline with the chainriung on the outside, and there's typically a 5mm difference between inside and outside.

Measure twice, buy once.