Originally Posted by
maddmaxx
Is your front derailldur a modern "road derailleur". In other words, is the cable pull arm above the pivot screw about half the length of the arm between the screw and the cage or is it about the same length. If the latter then you have the wrong "ratio" in the front derailleur to work with STI levers and will need a new FD. Might not be the problem but the check is quick.
edit: this is the same symptom as when running an MTB front derailleur with road shifters.
Thanks for this explanation. It looks like I do need a new derailleur. The one I have is an old road derailleur (RX100). The arm lengths are pretty similar...just over 2 cm above and 2.5 cm below...far from being half the length.
The problem still happens even when I changed the cable routing to under the tab and even when I push the lever all the way across, ignoring clicks. I have to push all the way across twice. I even turned the derailleur round a bit to give more of an angle to the cage which helped a bit but not enough to allow one push.
I think a new derailleur is called for. It seems upgrading one thing always leads to another thing. I hadn't planned on a new rear derailleur either but it turned out the 7 speed old one wouldn't move far enough to reach the largest sprocket.