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Discussion Starter · #1 ·
Trying to move chainline inward as much as possible for a 42/24 2x9 setup on my Dos Niner and as expected there is only a small amount of clearance between largest chainring and chainstay. Is there a recommended minimum? I currently have about 2-3mm and no problems so far with several rides, but want to give my frame the best shot at surviving if there is something I haven't considered.

Thanks in advance.
 

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Hack Racer
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I would put a piece of tape at the tightest spot and look to see that the chain rings don't ever meet the piece of tape. This includes hammering up a hill as hard as possible in a stupid hard gear to see if flex in the frame or flex in the chainset or a combination of the two do not cause a marking on the piece of tape.
 

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ups and downs
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How close is the crankarm to the chainstay? The arm is more likely to flex further since it is a longer lever, and you'd want at least 4-5mm of clearance to the arm. As Cheers! notes, the only way to know is to test to see if there's any contact, the clearance required depends so much on frame, BB spindle and crankarm stiffness.
 

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Discussion Starter · #4 ·
Plenty of arm clearance. As for ring contact under load/flex, that's one of the first things I tested. I also have zip ties placed as sophisticated (though affective) anti-shiftsuck devices at the spot suggested by Cheers! Seems to be contact free even with some heavy cranking.

So seems there is no general rule of thumb or "standard" clearance to shoot for other than make sure the (in this case) big ring is far enough away to avoid touching through "normal" operation (bent rings and other damage not withstanding here)?

Any thoughts on providing space for shiftsuck (dropping from big to little sometimes has trouble releasing - hence the anti-suck device mentioned earlier)? With the minimal clearance I'm thinking this may help reduce the occurrence or at least the affect since there is little to no room for the chain to fit in-between the ring and stay.

Thanks again for your input!
 
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