Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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Try adjusting the "B" screw to bring the RD up as close as possible to the cassette being careful not to be too close on the larger sprockets. That will improve shift response in all gears.
Also adjust the trim outboard a tiny bit. It's easier to compensate with a bit of overshift when downshifting, then on upshifts where the RD return spring does all the work.
Lastly if it continues to be a problem with one chainring but shift OK with the other, triple check the hanger alignment. As the RD cage rotates the upper puller swings an arc. If the plane of that are is off compared to that of the wheel the pulley will move in or out slightly depending on which chainring you're on. In your case it's moving in as it moves back, so tweaking the hanger front-in a hair may solve the problem. If you're skilled, stick an allen key in the upper pivot bolt and give it a nudge.
An ounce of diagnosis is worth a pound of cure.
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