I was looking at a tire size calculator at americastire and was wondering if someone could explain why a 235/45/17 tire and a 245/45/17 tire have different revs per mile? Why does the diameter size and sidewall height change due to section width?

 

235 = section width expressed in mm

45 = sidewall height expressed as a percentage of section width

17 = size of tire expressed in inches

 

It's a different size, that's why it would change. vvv

OP, this is the aspect ratio...so depending on each tire's section width size, the ratio would change.

 

Exactly.

A 235/45/17 is smaller in diameter than a 245/45/17.

The sidewall of the 235/45 is 45% of 235mm.

The sidewall of the 245/45 is 45% of 245mm.

That's why we get roughly the same diameter (but not exactly.....turbonut lol) going from a 235/45 to a 255/40.

 

Here's some reading:
http://www.tirerack.com/tires/tirete...e.jsp?techid=7

 

Ahh...that explains it...thanks

 

Thanks for the info