Alternative tire size

[hgevgili]

Hi I am looking for used snow tires. I found good 235-50-18 tires Pirreli 240s. These are a bit bigger than the ofiginal 225-50-18 (2008 G37 base). Does anybody know if they will be OK. What altrenative tire sizes can I use? Is there a degination for the bolt pattern, is it standard, do I need to look for sth specific on the bolt pattern if I find another set with the rims.
Many thanks in advance.

[Fezzik]

go to 1010tires.com to the tire calculator
http://1010tires.com/TireSizeCalculator.asp

input your original size and the sizes you are looking at. You want to stay within 3 percent change that it will tell you at the bottom.