As herrschaft said, it can be done with no real issues. .5" wider and 3mm offset difference isn't really noticeable and isn't going to mess up anything on your car. However, this also depends what size tires F&R you are planning for your "square" setup.

Putting bigger wheels in the front of a RWD sport car makes me question why you bought it in the first place though. If you're not after performance and/or are more worried about maximizing tire life, then maybe you bought the wrong car

FYI, in the winter I run 225/50/17 on all 4 corners and the rear rims are .5" wider. No issues with VDC or anything.

 

Well what do you propose I do? I am leaning towards 245/35/19F and 255/40/19R set up that's on there now...I just wanted somebody to expand on the idea of running a square set up.

 

If you want to test this square setup, then just swap your F&R's now and see what you think.

From what I think your needs are, I'd just stick with some value tires in OEM size and not swap F&R. However, it depends what YOU want. Figure this out, spend some quality time on the websites below and this should narrow down your options pretty easily.

Sizes:
If your goal is to have wheels that can be swapped F&R, then get tires of a similar width and diameter that aren't too different than OEM dimensions (so you don't mess with the VDC or speedo too much). This website can help you find sizes: http://www.miata.net/garage/tirecalc.html

Tires:
If you just want some decent/cheap/value tires there are tons of post on here and good info at www.tirerack.com (as already suggested)

 

By square setup I mean identical tire sizes: 245x35 front and 245x35 rear.....etc. If you plan on swapping wheel locations, there's one small bolt on each front assembly next to the studs that needs to be removed. Its only purpose is to prevent mechanics from putting the rears on the front since OEM tire sizes are staggered. I've ran that setup for over a year without issue.

 

I tried out 18x9.5 +24 wheels with 245/45-18's on all 4 corners on my coupe, and it looked and drove fine.

 

.....why would you put the rear wheels on the front and the fronts on the rear? just spend alittle bit of money and have a tire shop switch the tires and balance them if you're going with a square tire setup on staggered wheels when you want to rotate tires.

 

Why spend extra money when relocating the wheels works just fine, especially for those who go through tires rather quickly. Depending on camber wear this won't work for everybody and remounting the tires may be necessary.

 

^ this