I have a 2005 Giant Simple 7 that I love and ride every day. I bought it used and have no idea of it's history. I have had it about a year and put 2700 miles on it in that year. I think the chain is the original but am not sure but I decided it was time to replace it. So I go to my LBS to get a new chain and to make a long story short the guy wont sell me one unless I buy a new cassette as well. I insists a new chain will slip or jump teeth on the old cassette. I understand it is a good idea to replace them both at the same time but is it that critical that he is right in refusing to sell me only the chain? I have had many bad experiences in this shop but they have been in business for like 25 years so I just dont know what to believe.