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Trying to get chainring to work on my 29er. It's a Burgtec 30t oval. Fitted the 'right' way round (logos pointing outwards) it skips on the 10t (various chain lengths tried, new cassette and old cassettes and new chain) and is very close to fouling on the chainstay. Flipping it moves the chainline outboard, it's fine on the 10t (and appears to be on the 51t).
Is this likely to screw with anything else I haven't considered?
why not a BB spacer to move it out ?
That might be the longer-term fix, but concerned about the opposite crank being secure. And it seems to work as it is...
I can't think of any reason myself... Is it a NW ?
I think the standard chainring has the ridges to help it move up/down, but obviously you're running a 1X so doesn't matter... From what i can see the NWs are the same both sides...
I'd risk it... worst case it may knacker a chain quicker ?
Yeah it's a NW, I imagine that ovality won't change. Might try to get away with a tiny BB spacer though as the flip has moved it a few mm.
The trouble with that is, when you pedal your bike will go backwards.
The oval normally isn't symmetrical about the bolt holes, so I don't think you 'should' flip them. No idea what it actually feels like in practice though!
It's a shimano so direct mount with only one possible position either way. My brain is very small, but doesn't that mean you're at the same point of ovality at the same point in the pedal stroke?
Feels like that already. That's why I'm installing a 30t. 🙂
Is it the right offset for your frame - i.e. boost or not? If it is then check your BB spacers are in the correct position.
If it's not the right offset you may be able to move the spacers from one side of the BB to the other to improve the chainline (as indicated above) - as long as the total width of the spacers remains the same the crank arm should still be secure.
I can’t think of any reason myself… Is it a NW ?
Not now. Now it's a WN. 😁
Is it the right offset for your frame – i.e. boost or not?
Ignorewhat I said about this bit if it's Shimano as you say - the offset should be handled by the crank / spider.
Was the same crank working previously with a different ring? If so, is it possible you mixed up the BB spacers when swapping them? Can you put the old chainring back on to confirm it still works in the current configuration..
If you reverse fit it, can you use an old chain and return it to "as new" condition?
If the chain length is correct, then I would look at the lower cage pivot bolt, they arn't that well sealed.
https://nsmb.com/articles/shimano-derailleur-clutch-service/
Mech got a service at the weekend, so any remaining play is there for the duration.
If so, is it possible you mixed up the BB spacers when swapping them? Can you put the old chainring back on to confirm it still works in the current configuration..
The old chainring was fine (until I snapped a tooth off it, also this weekend).
Checking the BB spacers is not a bad call anyhow, though.
The oval normally isn’t symmetrical about the bolt holes, so I don’t think you ‘should’ flip them.
Yes, check the axis of ovality, see how it changes as you flip the ring
No idea what it actually feels like in practice though!
Biopace?
Burgtec do a 9-12 speed and a 12 speed only Shimano ring. 51 teeth suggests you’re riding 12 speed… but are you?
Yes, it's a 12.
Well we’re all gonna die at some point I guess
Mech got a service at the weekend, so any remaining play is there for the duration.
Did you pull it apart as per the link ?
Is the chain baggy in the 10t?
Yeah, full service. Was cleaner than I expected, TBH. Chain was set up as per Shimano instructions, which left it a tad baggy (and slipping), then took a link out with no improvement.
Not slipping with the reversed chainring, so it must be a chainline issue.
Well, update, it's not slipping on the 10t until the drivetrain gets damp, and then it slips as soon as you put any pressure on it. Tried shortening the chain again (probably a little too short for the 51t on full suspension compression now, tbh). Shifts perfectly in the stand, and for the first half-hour or so of the ride...
The only difference the reversed chainring makes is that it was slipping all the time with the chainring round the 'correct' way.
B-screw is wound right out. Low screw is correct. Hanger is straight. Chain is facing the right way.
Anything I've not considered? Or should I just try a different chainring again?
Just a thought, but has whatever damaged your chainring knocked the chainring spider out of true? If so this may cause the chainring to bolt up out of true. That mqy give your chain slip problem maybe?
Ian
Thanks - but it's Shimano Direct Mount, so no spider.
I would try another brand of chain. I had a brand new chain and sprocket from different manufacturers and they just would not mesh properly. A chain from another manufacturer was fine. Weird
I don't think it's a WN now, I think it's a SE.