Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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Whenever you have a large difference in chainring diameter, it limits the angle the chain can take coming from the outside. It isn't only a question of compact vs. standard but the number of teeth difference. It's function of the tangent distance from the smaller ring to the larger one. (that distance is proportional to the square root of the difference of the squares of the number of teeth in each chainring). In theory, with the same difference, compact drive's smaller chainrings would accommodate a larger angle.
As John said, you shouldn't be ride those crossed combinations in the first place, but if it's an issue for you, first check your chain-line, then consider moving the entire crankset outboard a few millimeters if possible. Note, doing so will worsen problems with the chain coming from inboard cassette positions, so it's something you want to think long and hard about doing.
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Last edited by FBinNY; 09-06-09 at 02:31 PM.