Originally Posted by Sportage EX
Is there a formula conversion chart to determine this? I know the middle number is a percentage of the tire width in mm. Were you doing straight math to figure this or is there a quick and easy app online?
There are converters everywhere on the Internet, but it's so easy, you may as well "Do The Math" yourself.
e.g. for 265/50-18
18 inch wheel = 18 X 25.4 = 457.2
Width of tyre = 265 mm
Tyre profile = 50%, so 265 X 0.50 = 132.5
Overall height = 457.2 + 132.5 + 132.5 = 722.2
mm or 722.2/25.4 = 28.43
Deeper treads will add a bit to this.
Effective diameter will be about 97% of the nominal diameter, so final drive revs per km will be:
1000/0.7222/0.97/3.1416 = 454
(or 1.609 X 454 = 730