Bicycle Mechanics - Missing one shift
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06-12-10, 02:16 PM
Dura Ace 10-sp. 53-39 with a newly installed Ultegra 11-28. shifts nicely except from 14 to 13 in the 53-teeth ring. New cable installed. LBS has adjusted it a couple of times. Works on the stand, but not on the road. New SRAM chain. I noticed the spring inside the RD was gunked up so I hit it with wd and a tooth brush. I don't think the hanger is bent. Any clues?
06-12-10, 03:18 PM
Any chance the derailleur is a little "loose?"
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.
Was the short housing at the RD replaced? This is often the site of excess friction. Housings should always be replaced with new cables.
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