So a couple of weeks ago I bought a Madone 5.1 with a 6703 crankset. Since I got it there has always been some noise in the middle ring (39t) but now it has gotten really bad. It is kind of a crunchy grindy noise. The chain is clean and oiled and it doesn't do it on the 30 or the 52 rings.
When the chain is on the middle ring the chain is dead center in the derailleur. Trim doesn't affect the noise. The noise exists on every rear sprocket and doesn't change.
I took it to the LBS I bought it at and they basically accused me of cross chaining and said that the FD was fine, even after I explained it occurred in every sprocket.
I'd like to have some ideas before I bring the bike back to them. It is kind of a crunchy/grindy noise. It *could* be that when the bike flexes the chain is swinging a bit and hitting the derailleur but like I said it looks fine when I get off the bike and look at it.
Has anyone run into this issue? Should I just take it to another bike shop?
If it is normal for the middle ring on the 6703 to make some noise I guess I can live with it. Would a 6700 52/39 be less noisy?
Thanks in advance.