On my last ride for seemingly no reason, about 5 miles from home I found I was unable to get into the inner chainring. It was almost shifting, but not quite with the chain rubbing on the outer edge of the cage. I thought a small stone had got lodged in the mech, so last night set about sorting it out.

There was no obstruction, so I thought I would set about re-setting it from scratch and this is where my problems have started. I have set-up the front mech on mountain bikes several time and never had an issue, but I cannot get this one to shift.

I’ve got a Sora triple shifter and a Sora double crankset. From what I’ve looked at online, you should set it so the middle shifter position corresponds to the inner chainring and the top position corresponds to the outer chainring. Setting it with lowest position to inner chainring, can apparently damage the shifter if you shift into the top position with nowhere for the mech to go, so you are better to have a slack low position that does nothing, with the middle position functioning as the ‘low’ position.

I have set the height and angle of the mech as best I can, and adjusted the limit screw so the inner cage just clears the chain when in the inner chainring/largest sprocket.
I’ve then attached the cable, shifted into the large chainring and set the other limit screw so the cage just clears the chain when in the large chainring/smallest sprocket.

But, when I try to shift between them, there doesn’t seem to be enough actuation between the two positions – even though the mech moves from limit screw to limit screw, the fact that on the inner chainring I have set the mech to the inner cage edge and the large chainring is set to the outer cage edge means that the mech isn’t moving far enough for the inner edge to push the cage onto the large chainring.

I have tried setting the outer edge further outboard on the limit screw, but this results in the chain being thrown over the top of the teeth.
I have tried adjusting the tension and this results in the chain shifting to the large ring, but then not back down again…..
I have also tried ignoring the advice about the shifter and setting the low position to the inner chainring, rather than the middle position, but this seemed to make no difference.

I have got the day off today, as we are having double glazing fitted so I thought I had plenty of time to get this fixed, but I have so far spent about 2hrs on it and am running out of patience.
I was hoping to get out for some miles this afternoon and tomorrow too, but at this rate I won’t be going anywhere!

I have looked at several online guides and as far as I can tell, I am doing what I should be doing. I don’t think anything is bent or mis-aligned.
Anything I am missing, or anything I should be doing!? I’ll be ringing my LBS and seeing if I can pop it into them in the next 30 mins if I get no joy!! The shame!

If you disconnect the cable from the mech does the chain then shift onto the smaller sprocket?

Yep, inner chainring never a proble; just getting it to heave onto the large ring that was the issue.

Took it to the LBS in the end. He reckoned it was just the cable tension, but I tried every permutation of that I could, from slackened right off to gradually getting more tension in it.
I think that it was probably that every aspect was almost there, but not quite!

I think I need to find some kind of ‘mech school’! Never quite sure if I’ve set them up by luck or skill!

Ah right, just your first line says “On my last ride for seemingly no reason, about 5 miles from home I found I was unable to get into the inner chainring”.

Ah. Sorry. Yeah, the initial problem was that I couldn’t get down to the inner chainring. I then didn’t really investigate why that was apart from look for a trapped stone.

I should probably have paid more attention when I ‘started from scratch’ to see why the mech wasn’t moving inwards as it should.

When I said above that the shop reckoned that it was just cable tension causing the problem, I mean for my failed attempt rather than the original issue.