Originally Posted by
JustinTNH
Hi there, recently my Dura-Ace 10-speed shifter (7900 model) broke, and I was hoping to find out whether other Shimano 6700/5700/4700 shifters are compatible with a DA 7900 groupset - mainly concerned with the Cable Pull ratio difference from such cross-build and Shimano's compatibility chart has been a bit confusing for me. Thanks in advance!
This might be helpful:
https://bike.bikegremlin.com/1278/bi...compatibility/
As I read it, the Shimano 8/9/10 road groups all share the same rear derailleur cable pull ratio. So most Shimano road 10-speed shifters should work with your existing RD.
As Bike Gremlin implies, there is one exception: the Tiagra 4700 shifter. The Tiagra 4700 rear derailleur is designed with the newer 11-speed road pull ratio, so the Tiagra 4700 STIs are designed accordingly. Thus, the Tiagra 4700 rear shifter
won't work with older 10-speed Shimano derailleurs. (The previous version 10-speed Tiagra RD and its shifters - the 4600s - are designed to use the original pull ratio, so that shifter should work with your existing RD.)
FWIW: I can confirm that the 4700 shifter works with Shimano
11-speed road RDs to shift a 10-speed system. I'm currently running 4700 STIs on one bike with a 11-speed 105 derailleur (as I recall the Tiagra 4700 GS was out of stock everywhere when I built the bike and I didn't want to wait months to complete it, so I used the RD-R7000 instead). But you also have to use a 10 speed cassette for that mixed setup to work properly.