[bdamschen]

are the 9 speed cassettes the same width as the 8 speed? can I put a 9 speed cassette on a rear hub that had an 8 speed prior?

 

[jrfor0]

yes. also, most 8 speed derailleurs can also be used for 9 speed stuff. you just need to toss on a 9 speed shifter

 

[bdamschen]

Awesome, that was my next question, thanx!

 

[Quo Fan]

You need a 9 speed chain, too.

 

[LordOpie]

How old is the drivetrain?

You may need to replace the front chain rings cuz if they're stretched out, they'll serious reduce the lifespan of the new cassette and chain.