So Old Man Winter is on his way to my neck of the woods and I believe that I am going to need a set of winter tires for my G37x. I went to tire rack and browsed their Winter Tire/Rim packages, and was a bit disappointed to see that the General Altimax's were not being offered. I had these on my last car and they were phenomenal in even the worst conditions, not to mention cheap! It appears that General doesn't make these in anything over 17".

So since my car has 18s on it now (225/50/R18 Good Year Eagle LS2, Front and rear), I am wondering what the options are for me to drop down to a 17" wheel. Would I need to get something with a higher sidewall to compensate? If I did my math right (0.5" = 12.7mm...50+12.7 = 62.7...rnd down to 60), I would be looking at something like a 225/60/17, which General offers in the Altimax, listed for $118/ea on TR. Will a 17" rim even fit on this car, or am I going to have to go with 18's to insure I can get around the caliper/etc.

I did a search here on the forums but with such an array of different g35/g37 models this has been discussed for already, I just couldn't find any concrete answers to this query, so I appreciate any input and help! Thanks!

As long as the 17" wheel clears the factory brakes then, yes, you can downgrade to 17". I use this tire calculator to determine what tire sizes work when scoping out new rim/tire configurations:

http://www.miata.net/garage/tirecalc.html