Alright, so after all the searching, I think I'm actually more confused then when I started off lol.

The wheels I'll be getting are 18x8.5 with a 44mm offset, and weight 22.5lbs. And from what I can conclude is that I should be fine with this set up with no need to roll my fenders. The tires I'm considering are Yokohama advans s4 or S drives, in 245/40/18.

So how much will I be screwing with the the cars odo? I think from switching from 225 on my stockers, to 245 on the new rims, I'll be adding an extra 100 miles for every 1000 miles I drive right? What would be the most efficent size tire should I slap onto my 18x8.5? I don't want to stretch my tires hence why I decided on 245s.

Now if the 245s are stretching, would getting 245/45/18 help increase comfort? I read that 245/40 does cause a bit more oversteer when hairpins or tight cornering is met. So would the 45 sidewall help keep it stable because of the extra flex? I just want to keep it pretty neutral like the way it is now with my stockers.

I've no plans for tracking my 8 but do run alot of spirited driving. Its really more of a weekend grand tourer that tackles a few twisties for fun. But I might give auto x a try down the line.

 

100 extra miles for every 1000 miles? LOL! that's excessive

going from 225/45/18 to 245/40/18 will add about half a mile to your tach for every 60 miles you drive. use this http://www.miata.net/garage/tirecalc.html

that tire setup is about as close as you can get to the stock tire diameter while using wider tires for our cars.

 

haha oops Alright I guess I'll give a +1 for the 245/45 then

 

245/40 is what you mean. 245/45/18 would mess up your speedo more. 255/40/18 is the same diameter as stock, while 245/40 is within a percent or two.

 

245/40/18 there's a reason why lotta ppl choose this over 45

 

yea, looks like I've got my answer lol. Thanks again everybody.