Can I change tire profile on my 2007 MX 5? Assuming I will have the clearance I would like to go from the low sidewall performance tires to the higher sidewall tires to increase circumference and mileage. I knoow the that this will affect speedo but I use GPS for metrics anyway. I'm not even sure the wheels accept a different ratio [more conventional] tire.

OK go ahead and yell at me.

 

If your only reason to change tire size is to bump your fuel economy, don't bother, any change you may get will be virtually immeasurable.

 

Thanks I kinda knew it. one inch change on diameter would give me 3.14 inch more per turn or about 3% gain, maybe 0.75 mpg boost.

 

Nope, more like a 0.01 boost (if that much).