Charlie Whiskey

Would last generation's Tiagra (4600) shifters shift a Sora RD (3500) on a 10-speed cassette properly? I believe the indexing is done in the shifters?

Slash5

Indexing is done in the shifter but the derailleur pull ratio has to match. But almost any Shimano road rear derailleur less than 11 speed will work with almost any Shimano road shifter - certain old Dura Ace being the exception. Any Shimano MTB rear derailleur and shifter less than 10 speed will work as well.

alcjphil

I believe the other exception is the Tiagra 4700 10 speed group. I think that it uses the same pull ratio as 11 speed so that the derailleur could be upgraded to 11 speed shifters but would not work with older 10 speed shifters
I could be wrong however

Charlie Whiskey

Sounds like it'll work. Cheers.

Slash5

Googled that when I saw your post. Couldn't find anything definitive but sure sounds like you are correct. That is going screw the world up a few years down the road. Have to be real careful mixing and matching after so many years of pretty well anything working. Have to think of that buying used, swap meets.

alcjphil

Another way of looking at it is that the new Tiagra will offer a much less expensive route for riders who eventually want to move to 11 speeds. As long as wheels are compatible,and increasingly new wheels will be 11 speed compatible, it will only be a question of changing shifters, cassette, and chain instead of having to pretty much replace everything