Changing tire sizes will effect your handling/safety. I would NOT recommend. If you are already considering a bigger bike don't put a penny into the 250 beyond maintenance and upkeep. People want to buy stock used bikes! I had fun putting money into my '08 250r. In the end though, it was still a 250. That being said, now that mine is gone, I want another stock one. They are a blast. Not sure what other sites you are on but I liked ninjette.org and kawiforums.com.