Senior Member (Retired)
Join Date: Sep 2001
Location: Great North Woods
Bikes: Vittorio, Centaur triple; Casati Laser Piu, Chorus Triple.
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I have been speaking to Campa about their docs, which, if you are following them, can be misleading. In particular, the one for the rear der.
I refer to a 9s, NOT a 10s rear der. The instruction sheets I have - which go all the way back to 1998 - all say that you should put the rear der on the fourth sprocket from the bottom (counting the bottom one), and adjust cable tension using the barrel at the der to center the top idler teeth exactly on the center of that sprocket. [N.B. They do not tell you which chainring to be on, but logic says that for a triple - my case - the center one is ideal. My thinking is that a perfect linear chainline is what you want.]
In fact, it seems that if you do not use the center chainring, and do use the fourth sprocket, you can pretty much guarantee that your shift up to the fifth sprocket will display the behavior you describe at least half of the time. I can duplicate the problem every time (though the specific sprocket sizes could possibly also play a part) following the instructions.
OTOH, if you use the center chainring, and the fifth, i.e. middle, sprocket, and follow the rest of the directions, it works a treat every time.
As I say, this is only logical, so I have been in discussion with Campa to get an answer or a changed doc from them. As it happens, in a very old instruction sheet, it does say that if you do it their way and have problems, then look at the alignment of the fifth sprocket and adjust the cable to center on the idler. That bit disappeared from the doc several years ago for some reason.