Is it possible to change the freewheel on an older road bike to a cassette? I have a SunTour Perfect 5 cog freewheel and i'd like to upgrade to something with more gears because i'm moving to the mountains. I know i'd have to change the hub, but i need to anyway. I guess what i'm getting at is, will it work? I'd like to replace the entire drivetrain in the meantime aswell, should i go ahead and switch to cassette? can i do that?