Front mech adjustment

[Monsieur Remings]

I'm a bit annoyed with one of my LBS. I asked them to look at the shifting on my older bike among other things which they carried out commendably. It was a problem shifting onto the larger chainring in mid sprocket. Since it's come back however - and I'd already fitted a new chain and cassette - the new chain comes off regularly. I adjusted the upper limit, clockwise to move the mech position in, so far so good, but now the bloody chain won't shift down to the smaller chainring without difficulty...

So, the last few days I've been trying to find the right position on the upper limit screw to suit both issues but can't help thinking this isn't going to achieve a solution. Do I need then to alter the lower limit? I thought they were independent of each other (the lower and upper)?

And, more importantly, do I need to release the cable for either of these adjustments to take effect? When I've adjusted the upper limit screw before, I've always left the cable intact.

Thanks in advance and yes, I know I should take it back, but they're quite some way and I haven't the time.

 

[raleighnut]

They are independent of each other upper limit screw controls the throw of the mech out, lower limit screw controls how far the mech moves to allow the chain to engage the inner cog without "overshooting" and dropping the chain inboard. It is quite common for the cable to be slightly slack when on the inner ring as the limit screw "does what it says on the tin" i.e. limits the travel of the mech inwards, of course this is different on a triple when cable tension controls the middle ring.

 

[RecordAceFromNew]

As raleighnut said the H limit screw has nothing to do with the chain's behaviour at the middle or small sprocket.

If the chain refuses to move down to the small ring there are 3 common reasons:
1) L limit screw is stopping it - normally you can see if the screw is abut to the stop on the cage to see if it is due to the screw - if it is turning the screw counter-clockwise will help
2) cable tension is too high - if the cable is still taut when you are in the low gear then releasing the tension may help
3) cabling is gunged up so the mech's return spring is losing the battle - similar to 2 just for a different reason

There are other possibilities, like the mech being knocked and is out/rotated etc. For a fool-proof process this is excellent.

 

[Monsieur Remings]

Thanks folks, I'll try and adjust the lower limit counter-clockwise then. I was fairly sure like I said above that they are both independent but seemed an odd coincidence that it (problems shifting to lower ring) only started happening after fiddling with the H-screw.

I also asked them to check the cabling at the shop; both the gear cables are teflon coated but I do wonder whether they could be part of the problem. Maybe I'll try a bit of lube on the pivots too but helpful to know that the H screw won't affect shifting down either way...has to be a separate problem.

And just for clarity...can I leave the cable intact?

 

[raleighnut]

Thanks folks, I'll try and adjust the lower limit counter-clockwise then. I was fairly sure like I said above that they are both independent but seemed an odd coincidence that it (problems shifting to lower ring) only started happening after fiddling with the H-screw.

I also asked them to check the cabling at the shop; both the gear cables are teflon coated but I do wonder whether they could be part of the problem. Maybe I'll try a bit of lube on the pivots too but helpful to know that the H screw won't affect shifting down either way...has to be a separate problem.

And just for clarity...can I leave the cable intact?

Yes but its possible that the shop moved the cable you should be able to see if they have by "crush marks" on the cable

 

[HB_Dude]

Try this, Great video...should help you get it running perfectly!

View: https://www.youtube.com/watch?v=tfBiXgf8JxI