First off, THANK YOU for any answers you can provide. I have read through the site but was hoping for a one stop all answer bc I am about to go batty trying to figure all this out.

I have an 05 Alabaster Roadster Limited Convertible, and it is my daily driver. I love the 19's but they are killing me in replacement costs. Hit a pothole or curb, tire has air bubble and is unrepairable.

My question - I've read that I can put 18's tires and wheels all around, or 17's on front and 18's on rear. If I go with the 18's all around, would I buy 4 of the same rims, or would I have to buy different rims for front and back? I know the bolt pattern is 5x112, is that all I need to know? Or am I missing the boat here entirely?

For tires I am thinking either (less than .5% variance):
Fronts: 225/40/18 or 225/45/17
Rears: 255/40/18 or 225/45/18

HELP!!!