9-speed sram cassette+ sram chain+tiagra shifter won't shift smoothly
I just bought a used 2006 Bianchi Castro Valley that has a 42 tooth chainring up front, and a 9speed sram cassette (12-26T) coupled with a Shimano Tiagra rear derailleur and SRAM chain. I discovered that the chain is noisy in certain cogs, so I tried adjusting the tension of the cable.
I had no luck, so I brought the bike into my LBS. The mechanic adjusted the cable tension, made sure the derailleur and hanger weren't bent, and put in a new SRAM chain and 9speed SRAM cassette. The shifting is still noisy.
I'm writing all of you to see if you have any ideas about the problem (or should I say solution?). Also, does anyone think that using a 10-speed chain might help?
Thanks in advance.