Originally Posted by Doctor Who

No, you don't need a new hub, just so long as you can replace the 7-speed freehub assembly on the hub with an 8-speed unit. The part cost me $24 or so.

And I'm using the original 7-speed chain on the 8-speed system, which is correct. The only difference between a 7 and 8-speed freehub is that the 8-speed unit gives room for the smallest cog.