Originally Posted by
Retro Grouch
Sometimes a too long chain will cause that. He fixed it by substituting a little bigger granny ring which took up an additional link of chain slack and ultimately by "cheating" a little on chain length for his big/big combination.
I wonder if he could have fixed it by substituting a longer B screw to pull his derailleur a bit farther back or by even reversing the B screw in his derailleur.
Maybe, but he said, "Set it up for Big/Big and with the
shortest chain possible and when I went 26/28 I had a problem." So was the 11-28 cassette new too, in addition to the smaller granny? I wonder if, with the shortened chain, in the big/big combo, the RD was pulled too far
forward causing the rub? Still don't get how the bigger granny fixed the problem. For sure, a longer B screw or flipping it backwards might have helped.