Biopace chain rings and front deraileur rub Turns out my front chain rings are biopace, after I thought they had disappeared!

I've got a problem with the chain rubbing the front deraileur at a certain point every rotation. I only get this in the highest gear on the inner ring and it happens from about the 4th gear when on the outer ring. getting gradually worse when changing up to the highest gear.

Not sure if it's a trim or height problem or both :S

when in the small inner ring height should not be a problem.



But it could be height issue when on the highest gears on the outer ring.

Setup


Dura ace deraileur front and back
105 cranks and chain ring
unknown back sprocket set
Keep in mind that there are 5 adjustments on a front derailer:


Low limit
High limit
Cable adjustment -- selects where the derailer stops for intermediate cogs
Height above crank
Angle on seat tube


For subtle chain rub problems sometimes adjusting the angle (very slightly!) is the best approach.

But remember that if the rub is only once a revolution it suggests that the ring, arm, or crank is bent.