Front derailleur won't shift into third (largest) gear

[bruin1989]

I have recently been trying to teach myself more about bike maintenance by doing the work myself (I know horrible idea ).  Recently I noticed that my chain was rubbing on my front derailleur so I went and altered the high/low screws on the derailleur.  Initially it wasn't moving when I was fiddling with the screws, and in an instructional video they suggested loosening the nut(bolt?) that holds down the shifting cable to allow the derailleur to reset to it's natural position before setting the high/low screws. I got it all going smoothly on the lowest (smallest) gear, and re-tightened the nut on the cable, but now when I try to shift to third it won't go.  Additionally the cable feels way too tight when I try to shift up to third.  I fiddled with it some more and managed toe get it to third, but I noticed that the red markers that show which gear it is in is way to the left, (far past) where it would normally line up with the 3 marker. I'm somewhat befuddled as to what has happened, though I have a strong suspicion I may have redone the cable improperly.  Any ideas?

[Joe_W]

(07-31-2016, 10:46 PM)bruin1989 Wrote:  [ ...] though I have a strong suspicion I may have redone the cable improperly.  Any ideas?

Sounds like - but doing your own bike maintenance is a good idea (so: welcome here!). You will do things wrong, but you will figure out how to fix them.

Sorry, the answer is a bit long (just went back up to write this..)

First, here is what you did wrong :p (don't worry, we all have been there...)
When the chain rubs on the cage in some gears it is usually a problem of cable tension (or of not trimming the dérailleur properly - or just an extreme combo that should not be used anyway). You should (likely) just have tightened the cable a bit more - as time progresses cables stretch.

I find setting up a front dérailleur (FD) actually more difficult and frustrating than the rear - doubly so on road bikes without barrel adjusters on the shifters. So: look at the video on this site. Look at one from somebody else. Think about what moves which part etc.

Here is what I usually do:
- shift down (release max. cable tension in shifter)
- loosen the cable, check chain rub on front: small / rear: large combo
- turn in the barrel adjuster at the shifter fully, back out two turns
- set upper and lower limit screws so that the FD can reach the uppermost and lowermost chain ring.
- on a 3x front, put the chain on the centre ring (or try to). The FD cage will wedge against it.
- pull cable taut and clamp it. Make sure you route and clamp it correctly! (yes, I know what I am talking about... can be source of cable tension problem)
- turn cranks, chain will drop to smallest ring.
- re-check chain rub in front: small / rear: large combination, it should just so slightly not rub
- shift to the centre ring (chain might not follow yet, just click enough ... eh.. clicks so the shift should have happened)
- if chain does not follow: tighten cable a bit and shift down and up again. You will get a feeling for how much you will need to tighten the cable if you pull on the exposed dérailleur cable by hand, redo until it shifts.
- check chain rub on large ring
- try to find the sweet spot of cable tension where shifting is crisp both up and down and the chain rub is minimized - while the above should be done on a repair stand (seriously, get one or build one), the last fiddling is best done on the bike on a quiet street / parking lot

I cannot really remember problems with the gear indicators - most of my bikes do not have them... so I guess it should follow "naturally"

Oh, and while you are at it (well, have loosened the cable), you might want to check the alignment of the FD cage. The outer plate should (on most - not all!) be parallel (seen from the top) to the largest chain ring when on the largest ring. The vertical gap (seen from the side) between the cage and the chain ring should be about 3mm.