 You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Followed the shimano setup doc, it does look like in in biggest sprocket I'm safe to take a link out, this will have the knock on effect of b-gap adjustment, chain wrap and angle the chain gets fed onto the cassette, things I know sram eagle is very, very sensitive to, important on the new shimano 12 speed?
I found the Shimano guidelines left me with way too much of a slack chain. To be fair, I think I've gone too far the other way but a trusty bike mechanic friend recommended that I deflate the shock, strap the swingarm up at maximum travel, run the chain through the biggest sprocket on the cassette and through the mech then pull the chain tightish and add a link back. That left with about 4 links shorter than the Shimano recommendation.
I've been running that way for a couple of months with no major issues. Can't quite get rid of an annoying click in one gear and I am right at the end of the B tension adjuster, so I think 2 links back would've been better.
No problems shifting up and down the cassette and no issues with the chain falling off.
strap the swingarm up at maximum travel,
wouldn’t that assume that the chain growth is greatest at full travel? Or is full travel usually where chain growth is greatest?
So there is a big long thread on weightweenies (can't find it just now but will update if I eventually do) that discusses chain length and associated noise and shift quality if you run the chain too short. Now this is specifically to do with direct mount style mechs which the 12spd stuff isn't(?) so it might not be totally relevent but having read it, adjusted my chain length on my road bike, which had hesitant shifting and was noisy, I sized my 12spd MTB chain the same way and it's been perfect.
Basically it surmisses that as the instructions say you should run the chain around big/big and add 1,2 or 3 links depending on how the chain overlaps. The thread claims that adding only 1 link is always wrong and that the chain should be run with 3 extra links instead. It also points out (as I found when i did it) that the different mech geometry means that the b tension works over a far wider range of adjustment than before. When i resized the chain to this longer length it was hanging slack in small/small, but a couple of turns of the b-tension fixed it and more importantly the noisy running was gone and shifting was improved.
TLDR: Run big/big without the mech and then add either 2 or 3 links and adjust with b-tension, the chain needs to be longer than you think.
Erm.. can't seem to edit posts anymore.?!
Anyhow, found the link. Worth a read and the conclusion worked for me YMMV obvs.
https://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=152332&hilit=chain+length
You've only got 15mins to edit a post.