[kingbobii]

im thinking about switching the casset on my rear rim from a 7 spd to a 9 spd and ive never done anything like this... other than the very obvious like a shifter what do i need?

 

[chicodude]

im thinking about switching the casset on my rear rim from a 7 spd to a 9 spd and ive never done anything like this... other than the very obvious like a shifter what do i need?

A new rear hub.

 

[kinghami3]

Because a 9 speed casset packs all the gears in more tightly, a thinner chain is required. You're going to have to switch almost everything to a 9 speed, this includes new rear shifter, new chain, new rear deraileur, new casset, and possibly new chain-rings up front (not too necessary but you might need to), and maybe even new front deraileur. The only thing that you for sure won't have to change is the front shifter.

 

[binary visions]

Yep, as was stated, you're going to need everything. You can probably get away with the front chainrings and derailleur unless they're pretty old (which they must be, with a 7spd).

You can sometimes find deals on "bundle" drivetrain parts at a place like www.pricepoint.com - where you buy all of the components in one package and they offer a discount.

You are going to need a new hub, though, so a new rear wheel might be in order depending on the age of your current rim.

 

[oldfart]

You can convert hubs. You will need a new freehub body and have to change spacers on the axle is all. New cassette and shifter and chain. The rear derailleur will work well enough, just watch that the slightly wider cage doesn't get too close to the spokes in low gear. You can probably narrow the cage with 9 speed pulleys and a little grinding of the pulley bolts. The chain rings might be a bit too far apart leading to the narrow chain not shifting as well and maybe landing between the rings now and again.

But if you have a 7 speed bike, it might be too old to warrant this type of upgrade. You might be better off investing in a new bike.