I've had my 06 Mazda 3 2.0 for almost a year now and have decided to upgrade on rims and tires. Im looking to buy 18 inch black Driv wheels and Nitto Neo Gen tires. Rim size is 18x7.5 and the tires are 225x40ZR18.. Ultra high performance rating. How will this effect my car... as in performance and the changing of the speedometer ive heard people say?... Do I need to change anything after I get these?

 

if the overall height of the tire doesnt change, the spedometer wont be changed (and if it did, you really wouldnt notice it...and you could use that as an excuse for getting pulled over..lol)

handling will definetly improve... cuz with the stock tires, there is more sidewall, so it flexes in turns.... putting on low pro's will pretty much eliminate this...
altho, if the rims are heavy, you may loose some acceleration, but not a lot..... since it takes more effort for the engine to get the larger wheels spinning

oh, and the ride may be a little bit bumpier.. since your riding on less tire.... but i like that feeling

 

+1

you're not gonna notice any difference. if the wheels are heavier than stock, then all you're adding is weight to the car. pretty much it. you could get into the physics and what not, but for a daily driver, it shouldn't make much difference

 

This should help ..
http://www.miata.net/garage/tirecalc.html