My rear cassette is an 8 speed 13-26 and I have to admit I am a bit confused on the different gear combos. I am not a technical rider by any means but having being off the bike for 3 years and training for a MS165 this Sept, I thought I would look into possible upgrades. You guys have been great and helped me not make any purchasing mistakes. I had read that most combos were 50/34 and thought that was the way to go.......shows you how ignorant I am . I do notice when I am climbing, I am in the 42/26 and struggling but when I get into the 30, I kinda spin too fast and I don't want to stress the chain by moving to the big gear on the cassette. Any suggestions?