Hello,
I am having trouble getting my 10 speed Chorus setup (2004 model) to
shift into the largest cog. Whenever I shift into the largest cog, the
chain moves there as it should, but as soon as I let go of the lever, it
falls back down in to the second cog from the top. I spent a while
adjusting the cable tension, thinking that I had the adjustment one cog
"off track" but this didn't seem to help things. After a while, I
realized that the lever would only make eight clicks in either direction
(being 10 speed it should make nine), so now maybe I am thinking that
the problem is with the lever itself.
I tried looking at the ratchet mechanism on the lever while shifting,
and it looks like at some point while upshifting the ratchet engages
into the wrong slot, thus throwing the shifter out of whack. Another
thing that leads me to thing that the problem is with the levers is that
for a while I was playing with the upper limit screw, and while I was
tightening the screw (bringing the derailleur away from the spokes) the
lever made a loud click, and the cable tension suddenly dropped to a
position corresponding to the derailleur being in the middle of the
cassette.
Does it sound like I need to rebuild the rear shifter? If so, would it
be a "traditional" rebuild (replacing the G spring, its washer and
holder), or might there be other parts that need to be replaced as well?
I would like to try and do the rebuild myself if possible.
FWIW, the lever has approximately 18,000 miles on it (many of them on
very hilly terrain, which means more shifting) and was rebuilt by a shop
~10,000 miles ago. I don't know exactly what they replaced, but I am
guessing they did a "standard" rebuild.
Thanks to all for any help.
Greg