What to do about spare tire

[Section_8]

MrElussive, the guy at the shop said that the size, comparing to the tire i have now, should be that if i was upgrading to 18" and thats the recommended size on tire rack also for the rim i want to get. What is the difference between the 40 & 45 series? now i'm getting all confused...

The 2nd # of the wheel sizes is the % in millimeters that the tire is high or 'tall'. The lower this # the lower the 'profile' (IE low profile tires, that look like yer riding on rim, or whatnot).

Example, 225/45/18 vs 225/40/18

Your 45's will be a little 'taller'. 45% of 225 is more than 40%, IE: taller tire (but not by too much).
I run 225/40/18 and am absolutely fine and enjoy the ride. A 45 will be a little gentler ride, because you are riding on more 'tire'. I've ridden on 225/50's before, honestly couldn't tell a difference between 40 and those old 50s, but I'm old and don't feel things as much (or hear as well either!)