Bicycle Mechanics - 8-Speed cassette on a 9-speed hub?

I recently replaced both the cassette and wheelset on my shimano 600 vitus. I bought a new 8speed cassette and have it on a new wheelset with I believe a Shimano Sora hub. Everything shifts fine *except* I can't get to the largest cog without the derrailer body bumping up/rubbing against the spokes (not overshifting into the spokes). I have adjusted it to the best of my ability but it just won't get to that largest cog without the derailler body (actually the pulley-wheel frame) touching the spokes. Do I need a spacer here? Is the problem that it is an 8-speed cassette with a 9-speed hub?

Many thanks!
alex

8, 9 and 10 speed hubs are all interchangeable with the exception of the 10 speed only Dura Ace hub.

I think the Shimano 600 derailleurs maxed out at 7 gears (this for the 600 Ultegra, pre-1998 according to Sheldon Brown (http://www.sheldonbrown.com/shimano.html)--scroll down to "Older Group Names"). You'll need to replace the derailleur to one compatible with an 8-speed drive train; I'd suggest geting an 8-9 speed derailleur, just in case you decide to add another gear in the future. (You do need to make sure the new derailleur is also compatible with your shifters.)

when you look at the derailleur, are the pulleys lined up vertically? If they angle in towards the wheel, then the hanger is bent. do NOT try to bend it back out using the derailleur since the derailleur is weaker than the hanger, it will break first.

I would make double certain that it is a bent hanger before trying to bend it back. It could also be just a bent derailer cage.