Quote:
Originally Posted by mmartahus
i have 225/45/18s on my stock gts wheels. they are a little wider but hold the road great! gas mileage is down 2mpg tho on the highway 
worth it for the added traction tho |
The reason your gas mileage is down is not the width its because you are turning a TALLER tire. Takes more energy to make one full rotation of that tire than it would a 215/45/18. That and your mph is going to be off either -/+ depending on if your tire is taller or shorter than the oem one.
a 225/45/18 tire is 225mm wide/i believe 45% of 225mm is the height of the sidewall/18" rim diameter.
so a 215/45/18 tire is going to be a little shorter if you set the 2 next to each other. Since you are at 45% of 225 instead of 45% of 215.
If you change to a 225 tire or larger the rest of your aspect ratio needs to change also. a 225 tire you might be better off with a 225/40/18 or maybe a 225/35/18.