Question is what the title says. Thanks.

 

Most Likly 8"

 

If it is 8" then how can they fit a 275 tire on it? I have conflicting numbers. I have seen both 17X9 and 17X9.5.

 

your talking about the 10spoke SS wheels? They are 17x9.5"

 

are they really? i could have sworn mine were 9. you can get a 295 on a 9.5 right? any bigger?

 

they should be 9", and you can put a 315 on it if you want, but I wouldn't.
I drove my friends 99 SS with 9" ZR1's with 315 Nittos DR's on them and the *** end was really squirrely when I was shifting, had 18psi in the tires.

My brother has a pair of 315 BFG G-force KD's on his 9.5" Z06 Replica wheels and they don't seem that bad since they are a street tire and run at 36psi.

Personally, I'd go with a 285/40/17 tire.

here is the 315 KD,

 

So which is it? One is saying 9" and another is saying 9.5". Also to measure it, is it as simple as taking a tape measure and going from lip to lip?

 

over at SLP, they list them as 17x9,
http://www.slponline.com/view_product.asp?P=80093

 

bead surface to bead surface, or in most cases they have a 1/2" lip and then you can do lip to lip and subtract 1". If I remember right, all the 4th gen 17's are just slighly under 9" (actually made to some close metric size or some such BS).