I replaced my chain today and during the test ride a problem became evident. When riding in the the middle ring gear there is a grinding, ratcheting feel with an audible crunch noise. This doesn't exist in the small or large ring gear (which I use very rarely) only in the middle.
Nothing is rubbing or making unusual contact anywhere along the derailleurs or anywhere else. I'm supposing that the same wear which necessitated replacing the chain is also prompting me to replace that middle gear too. Does that seem reasonable, likely, certain?