Originally Posted by telegooner
How can 265-70-17 be smaller. What do each of these convert to in iches i.e. 33's or 32's?
First number (255) = tire width
Second number (75) = percentage of that width for the sidewall height
Third number (17) = diameter of the opening for the wheel
So, the 255 is a millimeter measurement. If you multiply that by 75%, you get 191.25 millimeters for the sidewall. If you double the sidewall (above and below the wheel), you get 382.5 millimeters which converts to 15.051". When you add the 17" wheel, that brings your total diameter to 32.051"
Using the same math:
70 percent of 265 is 185.5. Times two (above and below the wheel) is 371mm or 14.606". Add the 17" wheel to get 31.606"
So, by pure math, you can easily run a DuraTrac on your stock wheels.
In real life, your 255/75R17 don't quite measure what the math indicates.
I've come to the conclusion that my OE tires, when new have a diameter of 31.8".
You can see how here
You can also see two members (flyinion and jsb432) who currently run those tire on their stock JKUs without issue.
On your stock wheels, you can run the 285, but could run into some rubbing when you turn and flex (offroad).
The threads referenced above will help you out. Once you grasp the metric sizing, it becomes easier to understand. It took me awhile, but one day it "clicked" and now things make more sense.
Enjoy the new Jeep.