Ex Racer, frame builder
Join Date: Nov 2004
Location: NSW Australia
Bikes: 1872 Rudge, 1902 Rudge, about 12 or so self built
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When setting up a fixed gear you should get it in line within about 3mm either way.
The chain runs so much better when its not scuffing on the sides of the chainring.
Its best to use a stiffer 1/8th chain even if you still use the thin ring / sprocket.
I've found that frame offset, wheel dish, BBaxle offset, and crank fitting position all interact to make it impossible to predict the outcome.
Best is to fit up all your bits, sight along the chainring back to the sprocket, and decide...........
Also sight along the rear tyre to down tube, and rear tyre to toptube to check that the wheel is sitting straight in the frame.
is it all OK ? .................. you're very lucky!!!!
is it fixed by putting the chainring on the other side of the spider ?
is it possible that your chainring is dished and can be turned inside out?
is it possible your sprocket is dished and can be turned around ?
is it possible to reduce the frame offset and increase the wheel dish? Or vise versa ?
is it possible to change the BB axle to a shorter / less offset one ? Or longer one ?
If none of these help, there are a few more "crude" methods available.