Originally Posted by
DiTBho
hi
suppose you have
- a Campagnolo 8 speed rear derailleur, say a Mirage short cage
- a Campagnolo 8 speed dx ErgoPower, say a Mirage one
- a Camapgnolo 8 speed sprockets cassette, 8 cogs of 1.9mm and 7 spacers of 3.1mm
I have the following doubts:
- How many mm does the rear derailleur cable move each time you change gear with Ergopower?
- How much force (in Netwon unit) is needed to move the rear derailleur one click?
I've ignored all of the previous posts in this dysfunctional thread due to the excesses of ego and drama.
Answers: Campy 8-speed cog spacing is a uniform 5.0mm cog center to center. The actuation ratio of this generation of Campy derailleurs is 1.43 : 1. That is, for every 1mm of cable pull, the rear derailleur moves on average 1.43mm. Which by division, it means that the average cable pull per 'click' is 3.5mm.
Yes, I know these are averages, but if you use these numbers to test for derailleur/shifter/cogset compatibility, and the math works, then the system will work flawlessly every time. I've matched up all kinds of official and unofficial indexed system combinations, and if this simple math works, then the indexing will work.
Cable tension: I haven't measured. If you are running 8-speed Ultrashift shifters with compatible derailleurs, then you don't have to worry. The Ultrashift derailleurs have stiffer springs, and work better with the matching shifters. As far as the Powershift and Escape models: you don't want those.