Problem shifting from middle to granny

[yello]

I fitted new chain & chainrings yesterday. Now maybe only 1 in 10 changes from middle to granny works; the chain just dragging along the mech for the other 9 attempts. Oddly, I can go from outer to granny no problems. Outer to middle works fine too, as do all changes back up.

When the chain is on the inner, it runs smoothly, no dragging on the mech. So I figure the mech is correctly positioned.

Any ideas?

 

[Renard]

Adjust the low setting screw. Or try slackening the cable slightly.

 

[jimboalee]

This is where Releasing Oil works.

Clean the front mech pivot bearings. These are prone to getting shitty.

Remember to exercise the front mech through it's range while you are warming up in the first mile of every ride. There's nothing worse than getting half way up a hill, flicking the change lever and the mech doesn't move

 

[mr Mag00]

Clean the front mech pivot bearings. These are prone to getting shitty.

+1

 

[yello]

Cheers jimbo, I'll give that a whirl. The mech is mucky (most of my bike is!) so that's a possible. Can I use WD40 (the horror, the horror!) instead of releasing oil?

 

[yello]

Nope. Took the mech off completely and cleaned it up, giving it a good clean and light oil at the pivot points. Re-fitted it and... no difference!

The only difference is that I've gone from Campagnolo chainrings to TA... but that really shouldn't make any difference should it?

 

[Dayvo]

Your front limiter screws might need adjusting.

 

[mickle]

TA rings have less pronounced chain release ramps than Campag, the new middle ring's taller teeth are holding on to the (new, less flexible) chain where the old one was happy to let it go.

Check that the outer cage plate is perfectly parallel with the chain ring and that it's lower edge clears the top of the chain ring teeth by no more than 2mm.

Pop the chain onto the middle ring, release the cable from its pinch bolt and then undo the inner limit adjust screw until it drops into the granny. This re-establishes the resting position. Reattach the cable and you're away.

Hopefully.

 

[yello]

Thanks mickle, that makes sense. I thought it had to have something to do with the new TA chainrings. I'll have another go at getting the mech positioned correctly. I reckon it has to be mm perfect!

A question....

Pop the chain onto the middle ring, release the cable from its pinch bolt and then undo the inner limit adjust screw until it drops into the granny.

...does the inner limit screw need to be done up before I do that?

 

[mickle]

...does the inner limit screw need to be done up before I do that?

No. No point screwing it in when you suspect it needs to back off a bit.

I assume you've tried downshifting with the cable tension backed off all the way..

 

[yello]

I assume you've tried downshifting with the cable tension backed off all the way..

Yes. I think the problem is that the chain won't come off the middle ring rather than it not being able to reach the granny. That's why your description of the longer TA teeth made sense. I figured I might need to lift the mech a bit to compensate... maybe.

I can change directly from outer to granny, and have even had the chain dropping off the inside of granny ring so I know the mech can reach it. I'll have another play tomorrow. Failing that, I'll take it to an LBS for them to have a look.

 

[yello]

Got it sorted after a fashion. I took it around to a club mates house and we both scratched our heads a bit, micro-adjusted cable tension and limit screws.

The mech was at the right height, and was parallel to the chain. Limit screws and cable tension were fine. It all SHOULD have worked. He'd watched the chain and mech and thought the chain only needed a gentle nudge for it to drop to the granny...

... so he decided, being older and wiser, to heel-in the mech a couple of mm... and it worked!

We could only figure that the chain was just that little bit narrower, or the new rear wheel (and hub) had ever-so-slightly changed the chain line to make that couple of mm make all the difference. I get chain rub if I cross block but that's hardly a problem...shouldn't do it anyway! I'll put a few hundred km on it and maybe that'll free things up a little.