Originally Posted by Bike4Him
I have a 2012 Ultegra drivetrain and a 12-27 Ultegra cassette.
Shifting is great from the big or small ring through the lowest and highest gears.
In the middle of the cassette I sometimes have to shift twice up or down to get one cog change.
I can usually just push on the brake lever a little past the "click" to go lower, but then sometimes I go to far.
Anyway, it's annoying and I can't figure it out.
AGAIN,
WHAT is the incline of the roadway when the shifting is balky?
Roughly, how fast-or-slow would you say the bike is moving at the time?
No offense, but if you cannot be more specific about the conditions other than to say "sometimes" AND if the solutions which have been offered have not pointed you in the right direction, then your query is almost as meaningless as asking whether it will rain on October 14th.
Quote:
Originally Posted by
oldbobcat .
You have already replaced the cable and housings, and the openings in the housings are open, and the cable loops are nice and round, and there is nothing compressing the cable or cable housing, right? And if the routing is inside the frame, there's no chance that the front and rear cable are crossed? And the cable is correctly routed out the back of the stay, and all housings are firmly seated in their ferrules? And, by the way, shifting is often better if you route the cable around the outside of the handlebar, not the inside.
Because the problem only presents itself around the middle of the cassette, not the slow end or the fast end, and the spring drops the chain down to smaller cogs promptly (presumably), I'm starting to suspect the lever. Before giving up on it or submitting it for warranty replacement, here's my suggestion. Replace the cable and spray the inside of the shifting mechanism with an aerosol solvent. Let it soak and drip for a few minutes, then work it around by trying a few shifts. Then let it dry, or speed that up with compressed air, and then load it with a foaming aerosol lubricant. Sheldon Brown recommends lithium spray grease.
If this doesn't loosen up something foreign in there, I'd suspect worn ratcheting splines, which could turn into a warranty case.
GEEZ ...
While it certain could be a warranty issue, the shifter is only 1+ year old ...
Time to consider CAMPAGNOLO SHIFTERS!!!
Of course, THAT comment is to lighten-the-mood after my chastising the OP for his/her ridiculously vague description of the problem ...
But, first ...
The OP needs to
try to confirm that the problem is NOT the Cassette by swapping the current wheel with another & isolate each component, individually.
THAT also means that the OP should have someone else try the particular wheel/Cassette on another bike.
ALSO, when the problem occurs, then s/he should turn around and replicate the "moment" by riding across the same roadway AND executing the same shift, again.
