Originally Posted by
zacster
Is Tiagra any different in front? I never understood why they made this one line somewhat incompatible with the others.
I believe the answer is yes for Tiagra 4700 and the 11 speed left “shifters”.
Anyone can correct me if I’m wrong.
I believe Shimano made a change to their trim function on the inner chainring. For years the FD would shift down, to the low limit screw, and you could run the lowest (inner) cassette cogs without needing to trim the FD.
I think that the new FD shifters shift to the inner chainring, but there is an additional trim that is needed to run the lowest cogs. From what I understand this was to prevent throwing the chain.
The older STI shifters don’t have this function. When you shift to the inner ring the FD bottoms against the low limit screw. So if there is some slack it doesn’t make much difference.
On the new shifters, I “think” the cable stops the shift and not the low limit screw. The low limit screw stops the trim(?).
John