Chainline question Shimano 1x11 BSA on 036 frame

[cmh]

Was curious if I had this problem - and I kinda do, but...



SRAM XG-1175 cassette, brand new KMC X11SL chain, but, possibly most importantly - the Absolute Black oval chainring which is offset inboard 1mm.

[carbonazza]

I have an absolute black oval too, the 34.
An old KMC X11SL, that should be replaced on Tuesday by a new one.
When pedalling backward for just a half rotation, the chain jumps down one sprocket immediately.

Thank you for the video, it gives me hope something can improve here !

I'll try some variations: I have older rings: absolute black 32, SRAM28 and 30.
With a new chain. Play with some shims, the rear derailleur setup, etc.

[cmh]

What's really funny is that loading the bike in the car today, the chain dropped to the second cog as I was loading it into the car. I laughed.  I also very rarely leave it in first, so this was the first time that's ever happened.

[MTB2223]

Found this youtube video. It's a 10sp Sunrace 11-42T cassette comparison to a 10sp XT cassette with a 42T OneUp extender cog. The Sunrace (10sp) had the same back pedaling issue as the 11sp XT M8000, but the XT 10sp with 42t cog does not have it. The problem is in the 42t cog of the sunrace cassette, which have a different tooth designs as the OneUp 42t cog.

Maybe the issue on the XT M8000 cassette is causes by the same 'bad' tooth design of the 42T cog.

[Carbon_Dude]

I still say it's not a problem, I've never noticed it on a ride.

[cmh]

I still say it's not a problem, I've never noticed it on a ride.

You say it's not a problem, I say it's not a problem - because it hasn't happened to us. I can imagine it'd be annoying - and therefore a problem - for the folks who do experience it.

Cleaning up the wife's bike yesterday I was running it through the gears and thought to check... if you have problems with the back pedal issue, you might want to check out the XTR M9000 group. She's got the XTR derailleur and cassette, a KMC X10SL chain (X11 fit a bit tight on the jockey pulleys, surprisingly enough) and a wolftooth Cinch narrow-wide chainring on RF cranks:



Didn't seem like that chain would drop off unless the bike was shaking or dropped while it was being pack pedaled.

[carbonazza]

X11 fit a bit tight on the jockey pulleys, surprisingly enough

How do you see that?

[cmh]

X11 fit a bit tight on the jockey pulleys, surprisingly enough

How do you see that?

When I put the X11SL on the bike, the chain wouldn't sit right on the upper jockey pulley when it was brand new. Switching to a wider X10SL fixed the problem. Even asked about it here. Just this morning I noticed an issue with the cassette, and had a spare on hand, so swapped that in, and while I was doing that I tried swapping in a new X11SL chain. Sure enough, the wear seen from the use up to this point had thinned the upper jockey pulley enough that it's no longer an issue.

Here's the original post.