So i am trying to adjust the front derailleur limit screws and cable tension, but i can't get it to shift smoothly. It is struggling to shift the chain to the smallest ring, especially under torque, but when the chain finally shifts, it falls out between the smallest chainring and the frame. Any ideas on how to fix this since it makes no sense?
Front derailleur struggles to shift to smallest chainring, when it eventually shifts, the chain goes too far and falls out
1can you give us more details about the parts on the bike? does the rotational and height position of the fd seem like it should be right?– Nathan KnutsonAug 9, 2022 at 7:29
2a picture would help. There generally isn't a need to adjust the limit screws unless you change the chain ring size. Why do you need to adjust them?– el_osoAug 9, 2022 at 7:34
1Go though parktool.com/en-int/blog/repair-help/… and parktool.com/en-int/blog/repair-help/… - With your description, my first though is cables, but could be a number of problems. If these don't help, come back and fill in the question with detail of what you tried.– mattnzAug 9, 2022 at 9:12
@el_oso they do creep sometimes, as does the cable tension adjuster on modern 105, which made for a complete mystery to me when a friend was stuck in the little ring a short way into a very long ride - we figured it out between us and tweaked the limit screws and cable tension in a pub garden at breakfast– Chris HAug 9, 2022 at 10:57
I suspect that you've pushed the limit screw too far, to get round a cable tension problem– Chris HAug 9, 2022 at 10:57
Although I suspect that this may get you into more trouble.....
Your front derailleur has a lot more adjustments than the rear. This is to account for different sized chain rings. Make sure that the height and the alignment of the derailleur clamp haven't changed.
To rule out the possibility that the cable or the mechanism isn't sticking due to grime build up remove the cable from the cable clamp altogether and test that the mechanism snaps back. If it does adjust your limit screws from there.
I did adjust it to 2-3mm over the largest teeth and so the cage is parallel with the rings. The cable is also smooth, i think the problem was with a bent cage? I tried a different derailleur and it worked a lot better. But does this sound like something caused by a bent cage? Aug 9, 2022 at 12:32
it's a possibility, yes. Is it also the correct speed derailleur? While I've personally had no issues mixing what was i think a 9 to 10 speed front derailleur. Mixing a 7 or 8 speed with an 11 speed might cause more issues– el_osoAug 9, 2022 at 14:54