Jens-<< I decided to convert my Trek 5900 from a Triple to a Double. So I got a Double crankset,
double front & rear derailleurs, and an Ultegra double bottom bracket (109.5).
After setting it up I've found that the 39-11 combination causes the chain to rub on the inside of
the big chainring. I assume this is a chainline issue. >><BR><BR>
IT IS NOT A PROBLEM...with 9 cogs and little doodads on the big ring, you will experience this when
in small ring and smallish cogs. It is NOT a problem that needs any solution othert than not riding
cross chained.
Jens- << Do I need to go back to using a Ultegra triple BB (118.5) even though the crankset is a
double? >><BR><BR>
Ya do and your chainline will be awful...front der may not work at all, or at least poorly.
Jens- << Can I simply avoid this combination and be OK, or I'm I going to always have extra
drivetrain friction because of a poor chainline? >><BR><BR>
bing, bing, bing, we have a winner. Check your chainline , a line from the center of the crank to
the 5th cog up, it will be an amazing straight line, parallel to the top tube.
Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"