Originally Posted by
Tim_Iowa
I have heard rumors that the 4700 rear shifting uses a cable pull ratio that is closer to Shimano's 11-speed road ratio, not their legacy "SIS" cable pull ratio. But I can't say that I can confirm that rumor through official channels nor through personal experience.
I do know that 5600 (and every other 10 speed road group
except maybe not 4700) uses SIS, so they're all cross-compatible.
So, any 10 speed 105, Ultegra, or Dura-Ace RD will index perfectly with your 5600 shifter.
For that matter, any 7-9 speed RD (road or MTB) will index perfectly with your 5600 shifters; they all use the SIS ratio.
@
Slash5 is correct; get the GS (mid-cage) rear derailleur for your triple drivetrain.
So any Shimano 10 speed mid-cage should work, except maybe for 4700. Interesting. That increases the shopping options.
The 7-9 speed SIS shifters would shift 7-9 cogs, right? They'd shift fine to that many because the index gaps are the same, but they wouldn't shift all 10 cogs, right?