I noticed this has come up before on the M8000 drivetrain, and the conclusion was to run spacers.. well. .my chainring has the spacers built in:
M8000 boost crank, 2mm? spacer on drive side
Blackspire chainring (30 oval)
Boost, XT 42 tooth
short chainstays, 415mm
it's hard to see from the pic, but the chain line is horrible, back pedalling causes the chain to drop 2 gears
not a big issue
but on my heavier wheels i run a deaore 51 cassette, and that seems to add resistance just pedalling, and a slightly audible grind...
i have clearance to move the spacer to the other side, bringing the chainring more inboard
any thoughts? or ignore it
If there’s room to move the chain ring inboard why wouldn’t you? Seems like it can only help
Tinker for sure.
Give it a try and report back, but...
back pedalling causes the chain to drop 2 gears
...is not unusual with these wider-range cassettes.
back pedalling causes the chain to drop 2 gears
…is not unusual with these wider-range cassettes.
Aye - and it often stops happening after a few miles.
Ahsat had this on her Stanton. Something about how Shimano label their chainsets, boost isn’t boost or something…..
Anyway, we moved the spacer across and it’s fine. She’s never noticed the pedals being offset
not owrried about chain dropping back, never noticed before now, am bothered about the reisstance i can feel on the larger cassette
yer, i half read.. the chainline is something extreme like 54mm?
im thinking i wont notice the cranks movedacross slightly.. incidently, im pretty sure i have foot rub on the crank on the drive side only..
Boost Chainline on M8000 is 53mm. Your offset ring will bring in in a couple of mm. Still scope to move it in further with chainring spacers - I got some Wheels Mfg ones for the same reason.
Mine was a 34T ring, so didn’t have spacers. Your current chainline will be similar to my amended chainline, but mine was on a bike with 445mm chainstays, so your super short chainstays will exacerbate the angle at extremes.
Try some chainring spacers - worth a go. Chainline on 11T may suffer, but arguably you’d want efficiency in your lowest ratio over your highest.
How do you measure Chainline?
edit, 425mm CS but still short
yer, im going to try the bb spacer swap first i think and go from there
how do you measure chainline? centre of BB to centre of chainring.. not easy to measure in the real world..
How do you measure Chainline?
Measure diameter of seat tube (with ‘vernier’calipers)
Divide the diameter by two.
Add the distance between the chainring and the seat tube.
you can get a little chainring that goes inside the main one, and a little mechanism that moves the chain onto it when you need to. This also has the advantage of not needing a dinner plate cassette at the back, maintaining a proper chain line, and reducing the steps between gears.
Its the future, you wait and see.
