jjyiz28

i know the 275 is the width in MM i think of the tire. 17 is the inch in diameter, but what is the 40??

98SuperSport

iTrader: (1)

your sidewall

BackinBlack02SS

iTrader: (7)

275 is the width of the tire in mm

40 is called the aspect ratio. It is the percentage of the width in sidewall height.

17 is the diameter of the wheel

Ell Ess Won

Think of Runflats as being like 10.

BackinBlack02SS

iTrader: (7)

huh

Ell Ess Won

Nothing, just trying to make things easy...smaller sidewall = lower profile.

Hugger Z

iTrader: (4)

BackinBlack02SS is right. 40 is the aspect ratio. It means your sidewall is 40% as tall as your tire is wide. So if you have a 275mm wide tire, your sidewall=275*0.4=110mm. And don't forget your wheel diameter is in inches so when you determine your rolling diameter you need to convert everything to mm or inches.

Ell Ess Won

If you're changing your wheels, this is a helpful tool in determining what sidewall diameter you want to look at so you won't have to change your speedometer reading.

http://www.discountpartcenter.com/tirecalc.html