Is anyone out there running w/ 15/40 gearing? I don't want switch out the front sprocket because of "potential" chain bind and premature wear issues. If I went up to a 41t out back would I have to replace my chain? I don't really want to replace my chain yet because it only has 1500 miles on it. Would adding 3 teeth out back allow me to keep my stock chain but get close to the equivalent of a 14/39 ratio?