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2x11. New cassette & chain, old (NOT ancient though) chainset.
Cahin runs absolutely fine right across the block on the outer chainring but inner one skips and tries to climb onto the outer on any of the 4-5 smallest cogs. (Repeat: runs fine right across the block on the bigger ring)
can this be chainring wear ?
(Chainline looks fine. hanger checked and not bent (and ought to affect both rings anyway) and this is not chainsuck - it's trying to shift up, not wrap around)
I'm wondering if it'll all settle down once the cahin has developed a bit of lateral play
Anyone got any suggestions ? Ta
(edit. All shimano, chain is on "the right way round")
If it's trying to climb onto the bigger ring, then the chain is rubbing up against the inside of the bigger ring and being picked up by the pickup teeth.
The chain already has all the lateral play it needs out of the box.
Chain line might look fine, but I don't think it is. Either move it outwards, or just don't use those gears.
Is the chain length right? Was this setup working before the new chain?
It could be that on the smaller chain ring, there is less chain tension so the chain doesn't get pulled down into place.
Is there any scope to slacken the rear mech off a bit so the top jockey isn't as close to the next sprocket?
Thanks.
In answer:
chainline is non-negotiable (well, unless I start pissing about) as it's a pressfit, full width BB. It's all shimano so should be standard (I know, I gave a hollow laugh when I typed that !)
worked fine previously
it's at the front, not rear so it's chain route from top of rear sprocket to top of front ring I don't think chain length or jockeys are relevant (as long as they're not massively wrong, which they're not)
Sounds odd, what size chainrings are you using? Is there a large difference between the two?
no, actually very small difference (I wondered if that was the problem but I can't see how it could be)
thinking I might try turning the outer ring inside-out to get rid of any influence of shifting ramps/pins/shizzle
Sorry, misread the OP, thought it was climbing on the cassette.
If the chainset hasn't been removed/refitted or changed in any way, I can't see how this could happen.
If the chainset hasn't been on this bike before, then a thin bottom bracket spacer might be all that's needed.
Where are you? I might have some spacers to suit.
Thanks onza, I've lots of spares so don't need a(nother) spacer. Thing is that it's happening on so many of the rear sprockets that I also can't see a mm or two offset making a difference to all of those chain positions.
I'm going to dismantle later, refit with a reversed chainring & cross my fingers. It may be that the new chain's just unveiling a load of wear that I hadn't spotted and I get to buy new rings (yay! 🙄 )
Bit of a long shot, thinking of possible reasons, could the new chain be directional?
I've yet to encounter this personally, I double-checked my new KMC x11-93 was uni-directional before fitting last weekend, but a very quick google suggest chainring issues if you fit a directional chain the wrong way around.
I suspect flipping the chainring will introduce issues with the shifting since the teeth are shaped to ease the chain on and off.
Can you verify that the chain is catching on the outer ring with the bike on a workstand? Look carefully at how they are engaging with the teeth on the inner ring. My hunch is that the inner is worn to the extent that it is allowing the chain to slide or twist around on the teeth rather than being engaged and held in line.