Can you exchange cassettes and put on a 9 speed?

Answer 1

Yes. You can either swap out the rings on the cassette (also called cog set or cogset), which can be difficult, or you can change out the entire cassette. As you might guess, there are some issues with the modification. In changing out some cogs, you won't have to change cassettes or derailleurs or anything else. Just be sure you have the correct chain length for the new setup. This is a fairly simple and straight forward modification, though removing and tearing down a cassette to change cogs requires some tools. Not the least of those tools is the chain whip to remove the cassette, but you might subcontract that work to a bike shop. Note that the individual gears might get expensive; replacing two or three might cost as much as a whole new cassette. There are some considerations that must be made when swapping out a cassette. First, if you're adding one with more gears, you'll have to insure your wheel (the hub, actually) will accept the new cassette. Some are threaded and some are splined. Second, you'll have to insure you have enough room between the rear dropouts. Lastly, you need to be aware of which cassette you're planning to install because some of them require that you put on a new, narrower chain to use them. The suggestions regarding the cassette swap set aside the issue you'll have replacing the derailleur and shifter. In general, everyone knows you can't shift through 9 cogs with a 5-speed shifter. A new derailleur and shifter can make things expensive. Is it possible that the old "non-indexing" shifter can make a comeback on your bike? Is a retrofit in order? Think this through and do some more reading before diving in. A bike shop is often willing to work with you to up your knowledge of the whys and wherefores of these two-wheeled machines. Use the link below to Sheldon Brown's site. He's one scary hard core bike guy, and he can teach you a thing or two about the technical issues.