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Single chainring setup questions.(4 posts)

Single chainring setup questions.Alex-in-Evanston
Jan 17, 2003 9:25 AM
I'd like to setup an old frame with a 9spd campy rear and a single chainring up front. I'll be using a downtube shifter for the rear and cowhorn bars with a simple
dia-compe brake setup.

My question is about the bottom bracket. What axle length will I need for the single chainring setup? I've got a UN72 110mm lying around. Will I be able to use this fellow?

Thanks,

Alex
re: Single chainring setup questions.ciclista5312
Jan 17, 2003 7:06 PM
Chainline depends on what crank you are using. Por Ejemplo, a Record crank needs a 102mm spindle, but a Veloce uses a 111mm. Depending on what crank you are using, try a BB that is 1-2mm longer than recommended and run the single chainring on the inside of the tabs (with single C/R bolts) in order to utilize the recessed CR bolt bed in the back of your small ring. This will push the single chainring slighly further out, centering it better for the full range of gears in your cassette. For the cleanest looking setup, get an inexpensive track crank like the Sugino 75 which just happens to use the 110mm UN72 you already own. Hope this helps
-dan
Chainline is the issueKerry
Jan 17, 2003 7:09 PM
If you want a "perfect" chain line, you would go for a BB axle that was 3 mm shorter on the drive side than what was correct for the double. Consider that for a racing situation, you might want a front derailleur installed to be sure the chain doesn't jump off in a high power situation when running a more extreme chain angle.
Thanks guys. nmAlex-in-Evanston
Jan 20, 2003 7:46 AM