Ok, please do not turn this into a DO NOT DRIVE YOUR CAR IN THE WINTER thread.
The Blizzak LM-22 comes in 225/45/18. Would I do any damage or anything to the car running this tire on the rear as well? Problem is that I can not find any winter tire that matches both front and rear sizes. I know I will have a tiny more wheel well gap, but is the overall tire heigh difference enough to make it a concern?

 

Do you have a track model? If not, you can always get cheapo 17 inch rims for the winter, along with Blizzaks that fit (235/50VR17s - slightly smaller, but should be ok to use for only winter driving). Have you looked at the Pirelli Winter 240s? There may be appropriate 18 inch sizes in that tire.

EDIT - Tire Rack has Michelins and Pirellis in the 245/45R18 size.

check here

 

You're way better off with narrower tires with a higher sidewall. Wide tires ride up on the snow. Narrow tires dig in.

Tire rack doesn't have a winter package for the 350Z yet. But for comparison I tried an M3. They recommended much narrower tires on 17" rims.

http://tinyurl.com/1ot0

 

Agreed. That's why I'd go with the 235s on the 17" rims. I'm ordering an Enthu., so I wouldn't have to buy the smaller rims, but Bobby may want to buy some cheapo 17 inchers for the wintertime. (as long as you don't have a Track, Bobby) I'd say go with 225s but I'm not sure how well they'll fit the rear wheels.

Anyone have a tire aspect ratio calculator, btw? Does Tire Rack have one? Thanks...

 

Tire height on the 245/45/18's are 26.681 and on the 225/45/18's it is 25.9724 so the difference is about as minimal as your going to get. Just that winter is 5 months here so I dont want steel wheels or cheapo rims.

 

This is for a performance model.
Checked out the total height for the 17's and they are a bit smaller then the 18's (even with the 50 sidewall) so I think this is what I am going to do (LM-22 225/45/18's all around) for the winter.

 

Are you putting winter tires on the included rims? Are you planning on changing tires back and forth on the same rims?

 

yes, I would like touse the stock rims both winter and summer. I dont want to buy cheap rims or steel wheels.