I am trying to fix the front shifting on a bike (not my own, family member). The original reported problems were inability to shift into 3 (largest), combined with a tendency for the chain to come off when going into 1 (smallest). Essentially, it was stuck in range 2, and I discovered it also would not go from 1 to 2 (after manually putting chain on 1).
I believed the problem would just be a case of adjusting the limit screws, which is something I've fixed in the past. However, this did not improve the shifting - while the derailleur appeared to be in position, the chain would still skip against 2 when going from 1 to 2.
I proceeded to read around a bit and then started to adjust the cable (it's a bottom design, at least I think that's the right terminology) to increase the tension, but still it would not shift properly.
Along the way I've tried various combinations of cable tension (at barrel and at nut) and limit screw adjustments, and still not had a positive impact. Really I should have probably sought help earlier on - I'm out of experience and I can't think of a way forward now. I think I've made it worse so far by adjusting the cable.
The symptoms right now
- The front shifter allows me to keep rotating it beyond "1" (i.e. off the scale), I'm not sure if this was happening before I started fixing the bike, or if I caused it, or if it's even a problem.
- When I move the deraileur manually, without the cable attached, it does appear to align properly such that getting both 1 and 3 should be possible
- The gap between the outer derailleur and chain when in 1 (smallest sprocket) seems to be acceptable and aligned with pictures I've seen
- I try to attach the cable again using pliers to keep it taut; after doing this, the shifter is sometimes so stiff I can hardly turn it; other times, it essentially works, but only from 1 to 2 (will not move beyond 2). In this instance, the derailleur moves, but not enough for the chain to actually jump onto 2.
Unfortunately I think I've got myself into a position where I've deviated so far from the original problem that it's hard to tell what's going to improve the situation and what will make it worse.
At present, the front shifter doesn't work at all. With the cable attached, and reasonably taut when in 1, I can move the shifter between "0" (as mentioned, the shifter seems to rotate off the scale...) and "1", and observe the cable moving at the derailleur, and some derailleur movement. However, I can't move the shifter past "1", and in any case, nothing I'm trying is actually moving the derailleur sufficiently to change the gear.
Where do I even start? I don't feel like this should be a complicated problem to solve, but I could really do with an "explain like I'm five" overview of things to try to 1) reset all the components so they work individually and 2) work together so front shifting works properly and is fully indexed.
I don't know enough about bikes to say what shifter it is except it's Shimano and has GripShift Max twist shifters on the handlebars, and they are indexed 1-2-3 with three distinct clicks (as opposed to my own bike which is labelled L-H and has no distinct clicks).