Originally Posted by jeffb502
Just to clear this up for anybody that may have used this as a guide; the 2nd number is actually called an "aspect ratio" and it is a percentage, not a measurement.
For example 245/75/r16 means the tire width is 245 millimeters, and the sidewall height is 75% of 245 millimeters which would equal a sidewall height of 183.75mm, not 75mm. The 16 is simply the diameter of the rim in inches.
To manually convert tire sizes without having to use an online calculator we can do the following:
Tire height for 245/75r16 would be calculated as follows:
Tread width is even easier: 245/25.4=9.65"
The 25.4 that keeps popping up is simply a conversion...there are 2.54 centimeters (exactly) in one inch, which means there are 25.4 millimeters in one inch.
I was reading thru just to see if someone corrected that.
I was gonna say, so a 195/70/14 has the same size sidewall as a 265/70/15?