With my 295/30's on back, my siz will actually be a little smaller than stock, as far as rotation goes. Sidewall with stock is 89.25 vs 88.5 with the new tires. found that by taking 255x0.35 and 295x0.30.So I'll be going slower than my car says....LESS tickets for me.haha.But it really should be within 1mph so I'm not worried either way.

 

Just adjust the sidewall ratio to stay within 3% and you'll be fine.

Use a tire size calculator to verify the overall diameter between two different sizes.

http://www.rims-n-tires.com/rt_specs.jsp

 

http://www.miata.net/garage/tirecalc.html


it will bearly make a diff. like 1-2 mph

 

actualy 295-30-19 is the same speed. check that site above ^^^^^^^^^^^^^^^