trent

I'm about to put 18x8, and 18x9 on my car, my question is, why in the rear tire size most people are going with a 255-35-18, as opposed to a 245-35-18 in the rear??? Is it because you get more tire to protect the rim, or to keep the speedometer close to the stock setup??

juniorsdad

many run the wider tire to improve traction, especially for the f/i guys
(note: to answer your other question, both tire sizes do not come close in matching stock)

trent

I was meaning....going with the bigger size tire's in the diameter I was hoping to put on, that my speedometer wouldn't be too far off from the stock setup with the 215-45-17 going to a 225-40-18, and a 255 or 245-35-18 in the rear, so I guess it would be far off to the stock settings that came with the car, so by going to the larger setup I need my speedometer calibrated?

juniorsdad

try this tire size calculator....
http://www.miata.net/garage/tirecalcold.html

rominl

iTrader: (4)

there are a lot of reasons. yes more tire and sidewall for protection. also it might match better sidewall with the front

Brandon@TR

225/40 and 255/35 are almost exactly the same OD as stock and as eachother. That is the reason for that size recommendation.