17 x 8J tire questions

[ooooolinooooo]

I currently running 17 x 8J rims with 225/40 tires, but I am tired of bad MPG and weak start. I am thinking to switch to 215/45, but I am not sure if it's going to look bad or cause any problem such as incorrect MPH. Any suggestions? Thanks

[bunkkaws84]

this has been discussed a million times as far as looks....

Not to be mean, but...

S E A R C H ! ! ! ! !

Has for MPH, anything bigger or small than then OEM diameter will throw off your speedo. Use a tire size calculator to figure it out like this one

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

And for MPG and launch, anything bigger than stock is usually heavier, and will lower MPG. If you want good MPG keep the stockers on, otherwise you gotta pay to play.