I find moving up or down one tooth to be very noticeable. The funny thing is... I use to run 42/16 because I have to climb some hills to get home... I would still have to get off and walk up at some points. When I switched to 48/17 for some flat land riding I found that I could power over just about anything... I haven't gotten off to walk since. IMO it is just a matter of finding your perfect ratio. Whenever I think about tweaking my ratio I'll try a friends bike or store bike that has that ratio on it, or barrow the parts. Right now I'm trying out 49/16 and I don't think I like it... tomorrow I'm gonna switch it to 49/17 and see how that rides