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Discussion Starter · #1 · (Edited)
Installed a new crank set on my Scale (Atik). When in the largest rear cog, the chain is falling of the middle chainring. It's not the chain (changed it). Could it be something with the chain line, or is it a bad chain ring? Running 2x9.
 

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Check your chainline and chain length. Could be chain too long and der. isn't tensioning chain enough to stay in gear. I believe the B-tension bolt on you der. will also add more tension if this is the problem. It could be as you said you chainline is too far outboard. Check it.
 

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Cath,

Sheldon Brown has a good chainline discussion here:

http://sheldonbrown.com/chainline.html

Not sure how mechanic savvy you are with derailleur adjustments, but his link at the bottom of that page for "Gears and Drivetrains" has very good starting point info on RD adjustments, to include b-screw info.

Cheers, Chris
 

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Discussion Starter · #5 ·
Confusing...

Thanks again!

I've checked the chain length and B-tension, and it's alright.

Thinking about it, the chain line should be even worse at the big ring. And the chain ain't jumping off the 44th, even on the largest rear cog.

The problem occurs at the 8th and 9th rear cog, 32nd front.
 

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Easy way of checking is to just jam a ruler or etc. between your two chainrings since you are running 2x9 and check where it lines up on your cassette. You want it to hit the middle of the cassette somewhat.
 

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Discussion Starter · #8 ·
Corrupt chain ring

You have been helpful! But none of these tips works, so I guess it's an ueneven middle chainring. Did install the granny ring, and there is no jumping problems on the small and big rings.
 
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