Originally Posted by demoncyclist
Khuon-
Don't bet the farm on that one. The nine speed cluster fits in an 8 speed space. The cogs are narrower and so is the chain. Use and 8 speed chain on an 8 speed cluster, a 9 on a 9 and so on.
DEMON
I have heard that it IS possible, and the bike will probably shift well on the stand, but I think that in real-world riding, the 9 speed would not be as reliable, in terms of shift smoothness and speed, as well as durability.