I must admit as functionally intimate as my relationship to my bike is - it is like an organic extension continuous with my body - I am ignorant, dumb when it comes to figuring out mechanical malfunction. So dumb, I am embarrassed to take it to the mechanic or even post in this anonymous mechanics forum. It is somewhat anomalous,weird because I am quite good at assessing and diagnosing in my professional life.
Anyway, abashed preamble aside - I have a Campy Record double set up. I am getting what seems to be, sounds like chain rub - especially noticeable when I am on the large chain ring and in the middle range of the cassette. However, when I am off the bike and spin the crank hard I do not see any chain contact or hear the noise. The shifting efficacy is unimpaired. I swear I cannot say if it is coming from the back or the front!
Any ideas to give me a clue?