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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It sounds like a chain line issue. it's likely that your crankset is inboard compared to the position of the cassette.
There are two common causes. Either your spindle is short for the crankset and the crank is too far inboard, or your frame is bent and the rear triangle is shifted to the right.
Start with a basic diagnostic by placing a straight edge against the face of the outer chainring on a secant, and carrying it back to the freewheel. Allowing for the distance from the outer face, to the center of the space between the rings, your straight edge should meed the freewheel about 7mm or so to the right of center.
If it doesn't line up that way, find out whether it's the spindle or frame, by checking each, measuring the chainline from the frame, and the frame via the string method (do a search if you don't know how these are done).
Two other possibilities.
If the initial crank to freewheel test passed, then your rings are too closely spaced for the chin, ie. a 7s crankset w/ a 6s chain. Or if it failed, but the chainline and frame are correct, then it's possible that the BB shell is twisted with respect to the frame's plane. This is very rare, but not at all unheard of.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance
Last edited by FBinNY; 04-09-14 at 10:01 AM.