When I went to my LBS to buy an IG chain I was told that the rear cassette was also worn. I was given a HG cassette sprocket Shimano P/N CS-HG41-7 and a HG chain P/N KMC Z72. I informed the bike mechanic that the front chain ring said "USE IG CHAIN ONLY". lbs told me that it "should" be okay. Was also told that the front chain ring was not worn to the point of replacement. Cassette installed, chain installed. Rear shifts flawlessly, front is making all kinds of noise when down shifting and up shifting from mid to granny gear. Also front heitates/slips before shifting into gear. Derailleur adjustment are good. Last night after I finished my ride the LBS was closed so I posted here like I posted many other questions. So my qusetions are....1) can a HG chain work with a IG chainring set Or.... 2) Is the problem worn chainrings?