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Need some advise.

When I am running in the small chain ring 39, and third from lowest cog 14, I start to hear a slight chain rub, which becomes worst at 39/13. I know that we are not suppose to run shifted in the extreme chain x's 53/25 & 39/12. Should not the bike run in 39/14 or 39/13 without rub, right? . . . Or is the short chainstays, which increase the chain angle at extremes, is causing this. LBS and trusted mechanic/friend looked over bike and said it was fine, that is font dr limits set fine. no rub is heard in the big ring except for 53/25.

39/14 does not rub in repair stand, only when a rider is on it.

please comment.
 

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Do you know how to use the trim click on the left shifter? It's there to eliminate the chain rub on the FD cage. If the chain is rubbing the big ring, that's a different problem. The short stays do make it worse.

The tip of a tooth on the big ring should be 47-48mm from the center line of the seat tube, if the chainline is correct.
 

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I've found that with compact cranks (I've run 50/34 FSA K Force and K Force Lights), if the chainline is acute you will get rubbing when on the smallest front ring to the smallest cog due to chain rub on the big ring (not the front derailleur). It's a consequence of the larger diameter difference between the big and small rings, and therefore not correctable but rather avoidable-- I'm not one to worry about cross chaining too much, but certain ratios can be a pain on compacts, such as the small to small.
 
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