Is my chain too long?

It could be.

I recently fitted a new 11 speed chain to an 11 speed cassette with a new 12 speed test mech.

I measured the chain as per Shimano instructions for 12 speed on a hardtail.

To get the set up line on the mech to line up with the cassette, I had to take another pair of links out.

(There was a whole mech hanger issue as well but that was independent of chain length).

Just realised I posted the least relevant picture 

This is the one:

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What's it like at the other end of the cassette? And what is the gap between the top jockey and largest sprocket like?

TBH it took me a little while to twig that modern Mechs are actually happier with more chain and using quite a bit of the range of "swing" on the cage.

The old trick of having a chain so short that the mech is stretched tight on the largest sprocket with the chain only one link away from snapping just doesn't work 

So long at the chain isn't actually hanging slack in the smallest sprocket, you should be able to tweak the B-screw and get indexing to work (assuming your hanger is straight). 

It looks like you could use a bigger chain ring. The pictures make it look like it’s only just clearing the chainstay at the front. 

At the other end:

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Agreed about chain ring but it's my partner's and she is used to that gearing. I can't remember if the chain was dragging before I swapped everything away from Dumb Dub.

How does the set up guide on the back of the mech look? Where is the B tension set? It looks like it needs less. 

I'm suspicious of the mech hanger but any 2020 model bike should be Shimano 12 speed compatible.

That just looks like 1/2 a turn of b screw away from being ok. 

Thanks all  Out and away from the bike. Will B screw adjustment lift the chain away from the chain stay in the 10?

Yes, if the mech isn't fully compressed which it shouldn't be looking at the other end of the range photo.

More B tension will add chain tension. However, view the setup guide from the rear. It may be that you need less B tension to get the marking to line up. That may need you to adjust the chain length.

I recently had a similar issue and found that the mech hanger caused the mech to swing too far back. Once that was corrected, the mech sat further forward and as a result, I needed a pair of links removing 

Yes, do what onzadog said first. Don't add lots more b tension if it's more or less right or you are on too much already or the shifting in the higher gears will be poor.  Is if your chain length is right and there isn't sufficient b tension then add some. If the b tension is right or too much then the chain is too long. 

Useful to see a photo of the rear mech in lowest gear - if there's no tension in the jockey cage spring (fully folded back) and the chain is slapping the top of the chain stay then suggest the chain is too long. When in biggest sprocket, can you still push the jockey cage forward?

As far as chain length goes I've given up on all other methods, I just undo one end of the shock/remove it if need be and cycle the wheel through its movement, and then make the chain as short as it can be without binding. Best result every time.

Simple yes from me. Unless it's going to grow a lot under suspension movement, arm should be further forward than that. This is my (11 speed) Deore derailleur in 1st.  

No amount of b tension is going to effect the upper chain run, its chainring size, what does the spec for the frame say on that?

2025 model is a 30t minimum, what is fitted?

blob: https://www.canyon.com/8827c18d-a763-4ed9-80fa-981a1d2face8

Update. 30t as per OE spec. A tweak of the B screw did resolve it and did create tension without cutting the chain. It now clears the stay quite nicely. But the window for good shifting is pretty small.

Shifting is OK but nothing to write home about. I imagine the combo of a new Shimano chain with a very slightly worn SRAM cassette (with a SRAM chain previously) is never going to be amazing but they might mesh a bit better with a few miles.

I forgot to remove the new grease on the chain too before lubing it, that's bad isn't it?

Thank you for all the help!!

How is the setting guide on the back of the mech looking? Seems to make a massive difference to 12 speed stuff.

How worn was the outgoing chain?

Posted by: nickfrog

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Indexing was very tricky. Is that because the chair length is wrong?

Could be. Unless the bike is up in a stand then you'll need a fairly low chair or stool to aid adjustment. 

^ 🤣

As for the guide at the back, I normally stick to it but having a 52t rather than a 51t my head can't compute which way it should be as the guide is obviously for a 51t. It's there or thereabouts but I needed to get a bit more chain tension anyway. The outgoing chain was at 50%.

I would have gone sram chain on a sram cassette too for 12s. The inner links are longer on a shimano chain which works for shimano cassettes but not sram. 

^ not sure about that. I have been using Shimano chains on SRAM cassette for a long time Inc 12 speed without issues. I can't use a SRAM chain with a Shimano crank set/ring anyway.

Oh, ok. I usually find that a shimano chain won't shift as well if I have put one on a sram cassette because I didn't have a sram one to hand. The sram chains also work ok on a shimano chainring if the chainring is a bit worn, or at least I haven't noticed any issues. There's one combo that definitely doesn't work then, probably a shimano chain on a new sram chainring. 

I agree with you that the shift is not quite as good. I might consider a SRAM chain if I can find a compatible chain ring that fits on my SLX and XT 12 speed crankset!

Posted by: Yak

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I would have gone sram chain on a sram cassette too for 12s. The inner links are longer on a shimano chain which works for shimano cassettes but not sram. 

In the end you were right, I was wrong.

Fitted a Works Component ring and a GX chain. Shifting is spot on, compared to Shimano chain on GX cassette. 

Not even sure my full Shimano shifted any better even under load.