I have discovered that when on the small ring and smallest two cogs the chain rubs the inside surface of the large ring. It's a Stronglight 99, 48/28 with shortest BB spindle projection on right side possible. Is that a known issue with wide range double arrangements? I haven't calculated the geometry (will undoubtedly do so), and I know that on this particular frame I skewed the BB alignment a skosh, in a direction that would exacerbate this issue (fortunately I know why). Still, I wonder if this is part and parcel of such a large difference in the diameters of the two rings. Anyone?
John Clay Tallahassee, Florida USA
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