I just got a new wheelset and am considering upgrading my Dahon Eco to a 9 speed rather than fit my 7 speed cassette. Besides a cassette and shifters what else do I need to get?
The Eco has a Tourney rear derailleur, would I need to change it?
Does the chain need to be changed to a thinner 9 speed one?
Do I need to change the crank/chainwheel?