Could someone please explain what is wrong with my chain/chainring?

I’m baffled.

I have a SRAM PC991 9sp chain and a Hope narrow-wide retainer ring, both nearly new.
The chain sits on the ring fine from about the 12 to 2ish position and then gets completely out of sync with itself, it’s half a link out by the time it gets to the 4 o’clock and then by 6 o’clock the narrow bits are trying to go in the wide bits of the chain and vica versa.

Old worn 9sp chain fits on this ring fine, brand new KMC 10sp one doesn’t. I therefore suspect the ring is at fault but that just seems really bizzare. What is happening?

Thanks,

Is it hitting the chainring tabs?

Edit. I fitted a new chain to an existing ring and the new chain was fouling the tabs where the old one was not. Both chains were kmc 10 speed.

No, I did check that, it was my fist thought too. It’s close, but it does clear them.
Cheers

Good call – looks like the tab at 11 o’clock-ish is proud at the RHS corner

Try some spacers between the ring and the cranks.

Is it only one link that knocks it out of sync or the whole chain?

If the new 9/10 speed chains you’ve tried are the problem then if they are not N/W chains then are they compatible with a N/W chainring? I don’t know the answer to this personally.

It’s hitting the tabs on the spider, no? You can see the link immediately above the 2 o’clock tab is deflected upwards relative to the previous one.

Possibly your old chain had stretched to the point that it could reseat in the subsequent teeth, whereas the new chain has exactly the same pitch as the base of the teeth so once it starts to ride up it’ll carry on doing so.

Stiff link?

If the new 9/10 speed chains you’ve tried are the problem then if they are not N/W chains then are they compatible with a N/W chainring

Huh? There’s no such thing as a non narrow/wide bike chain!

*Edit… actually I’ll qualify that. There are half link chains, but I assume he’s not using one of those.

If it’s a 9 speed chainring and 10 speed chain, then incompatibility issue surely. Does a new 9 speed chain work OK?

Ajantom, I’d counter that ALL chains are narrow wide! Who knows though, someone did once invent a 29er specific saddle. 🤯

How did you join the chain? Not s snap link that hasn’t snapped…?

Hard to see from the photo but are you one tooth out on the narrow / wide – i.e. the narrow chain link is sitting on the wide chainring tooth?

Also, is that the joining link at 2 o’clock? Again, may just be the photo, but doesn’t look quite right…

So what ti bike you end up with?

Take the ring off the cranks and try looping the chain around it. From that picture it looks like it will fit. Another vote for spider tabs…

take more close up images of this bit. as is currently, of the chain separately and of the chainring itself at this bit.

Need clearer images I think.

I think you have the chainring fitted the wrong way round. I would expect to see branding on the outside. There is probably built in spacing on the other side to stop the links fouling on the spider arms.

I think you have the chainring fitted the wrong way round. I would expect to see branding on the outside. There is probably built in spacing on the other side to stop the links fouling on the spider arms.

This.
The chainring is mounted the wrong way round, the hope narrow wide has spacers built in on the front face so the spider doesn’t interfere with the chain.
Also has Hope branding all over the front face.

Hello again,

Thanks for the input all.
So, quick update. I had checked for fouling on the tabs, it was very tight but there didn’t appear to be any contact.However, I did what submarined said and it fitted round the ring OK when not on the cranks, which does seem to indicate that the majority are correct and it is something to do with the tabs. So why would the old chain be fine and the new one not? That is very peculiar.
.
This ring is 30t, after doing the above and concluding that you must all be right and it is a tab problem I put the 32t ring from the other bike onto it and it was fine, again backing up the tab theory, but not explaining why one chain works and two don’t.
.
To pick up on dallas’ suggestion, that bit which is visible in Neil’s picture I have facing inwards, towards the frame. Should this be facing outwards towards the crank? If so I will need to put shorter chainring bolts on it.
.
And well remembered Tdog, I was on here 18month ago looking for ti frame advice. I did indeed get one, this is a Salsa El Mariachi Ti. Bought locally so I could have a test, from a guy who claimed to have done 120 miles on it, if he had they were road miles, it was immaculate. Swapped most of the bits over though, really nice ss now.
.
Cheers

Hope 30T and 32T are different in how they mount to the crank arms – as @nealglover’s photo shows, the 30T has tabs on the outside of the ring to push it away from the arms so the chain doesn’t foul them. They also need different chainring bolts.

From outside => inwards: crankarm; tab; chainring; frame

To pick up on dallas’ suggestion, that bit which is visible in Neil’s picture I have facing inwards, towards the frame. Should this be facing outwards towards the crank? If so I will need to put shorter chainring bolts on it.

Yes, that is the outside face, they do need different chainring bolts as mentioned above.

So why would the old chain be fine and the new one not? That is very peculiar.

Possibly your old chain had stretched to the point that it could reseat in the subsequent teeth, whereas the new chain has exactly the same pitch as the base of the teeth so once it starts to ride up it’ll carry on doing so.

If the chainring worked with the old chain when the chain was new then I guess it’s just a slight difference in shape.

I reckon the chainring should be fitted on the outside of those spider tabs as well as being the correct orientation.

Put the chainring the right way, it’s clear the spider is stopping the rollers of the chain bottoming out on the ring, it might appear fully engaged but its not, retainers work for 9,10 & 11sp so there’s no other explanation,unless you’ve accidently used superglue instead of chain lube.

Hello again,
.
Had another play with it tonight and you’ve cracked it, turned the chainring around it works fine. There is a wee spacer sort of machined into that side of the chainring which pushes it out from the tabs a bit.
So, the 32 and 34 both go flat-side against the tabs, but the 30 doesn’t. Very odd. Doesn’t seem to have affected my chainline though.
Stiff can’t understand why one chain worked and two didn’t previously, I would have expected all or none but hey ho, at least it works now.
Thanks all.

Old chain had a bit of slack in it, allowing it to “stretch” over the crank tab then fall back into the well of the teeth.