1x10 issue: chain disengages from largest cog when pedaling backwards

I

ItsWin

Member
Anyone else encounter this issue?

I'm currently running a 1x10 setup using a OneUp 42T cog and RAD cage on my Rune. 32T chainring. Everything works great except that the chain disconnects from the 42T cog when I pedal backwards. This doesn't happen on the other 9 cogs, just the 42T. It disconnects at the top, so I assumed it was a chainline issue. I got the chainline down to 49mm (the minimum on my Atlas EXI crank) but still no change. I was thinking of moving the 2.5mm BB spacer to the non-drive side to get the chainline even more inboard, but saw that with the 49mm chainline, the chain was already real close to rubbing against the chainguide plate in low gear, so no go on that idea.

This is my first time doing 1x and I can live with this issue if I have to. In every other way it works great. Shifting is excellent (RAD cage made a big difference) and I really don't lose too much of the gear range I had with my 2x9 setup.

It looks like there may not be a fix for this. Am I wrong in any of my assumptions?
 
Yes, it happens to most of us. Both of my 1x10's skip when you back pedal. Chainline is the issue and there's nothing you can do but design a floating chainring. You can mess with your BB spacers or get chainring spacers to move your chainring towards the part of the cassette you use most if you really wanted to.

There's no reason to back pedal so just don't do it. Back pedaling for pedal position in a turn won't be enough to throw it off.
 
It used to happen to me too. Not sure why it stopped. It has no bad impact, so I didn't worry about it.
 
I had the same exact issue last week, I replaced my BB, chain, took the casette off for a nice deep cleaning and when I put it all back together the chain would pop off on back pedal, I took it in the my lbs and had the mechanic re-adjust my rear dérailleur and took away the harshness of the chain popping off and after a nice long ride yesterday of breaking the chain in it seems even better.
 
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