Novice needs Boxster tire/rim sizing help
 

I have an '02 Boxster with stock 16" rims and am looking to upgrade to a larger size. I have a buddy that would essentially give me some nice rims and wheels and I have no idea if they woudl fit. The rims are nice 18" Anteras - rears are 10X18 with Bridgestone Potenza S02 285X30X18's and fronts are 8.5X18 with Potenza S02 235X40X18's. Would these fit without any modifications? Minor modifications? Would there be a performance hit or increase? Many thanks in advance for your thoughts and advice.

http://mike.focke.googlepages.com/willthosewheelsyouwantfit%3F

http://www.tirerack.com/wheels/tech/index.jsp
http://www.tirerack.com/tires/tiretech/tiretech.jsp