Originally Posted by
TnDiamondback
Will the RD not work on 10 speed? It is the shifter that determines the RD movement correct? The distance traveled from small ring to big ring is the same isn't it? Just more stops closer together?
These are questions, not statements as I continue my education on bike mechanisims.
Incorrect, you also need to consider the cable pull ratio. With Shimano, they have kept this constant throughout almost all their indexed rear derailleurs (early Dura-Ace is an exception) so any rear derailleur will work with any shifter. SRAM uses a different cable pull ratio, so you must match a SRAM shifter with a SRAM derailleur.