Okay right now I'm in the process of researching a few mods for my truck. For the most part i'm doing all right with everything but tires. What exactly does 265/70/16 mean. I know the 16 is rim size.

I want to put 31" tires on there, but whenever i go to websites for tires it seems like 31" tires only are availabe for 15" or 16.5" rims.

Any help would be greatly appreciated. The searches I ran on this didn't really help.

You already have 31" tires on there, they are 30.6" in diameter, which is right about what a 31" tires measures.

Your tires are 265mm wide at the widest point (the section width, usually halfway between the tread and rim).

The 70 is the distance from the rim to the edge of the tread expressed as a percentage of the section width (70% of 265mm, or 185.5mm).

Double that since it is a radius, and you get 371mm, or 14.6 Inches. Add that to the 16" rim, and you get a 31.6 inch tire.

You can check other sizes here...

There is a convienent link to right here on the XOC that can help you with that...

http://www.xterraownersclub.com/news.html

Click on Tire/Gear calculators...at the bottom you will see the metric to US Standard conversion.

For your question 265 = Width of the tire at the widest point (not the tread) in millimiters. The second part /70 = the percentage of the width of the tire that is numeric height of the sidewall. The last number is the wheel size (you already got that.

The only problem with doing a strictly mathmatecial conversion is that the sidewalls are never straight (they bow out), to the multiplier is a guide, not a direct size.

Basically the bigger the first number = the wider the tire.
The bigger the second number = taller sidewall (in proportion).

BTW those add up to (approximately) 30.61 inches in height - per the XOC calculator...Close to 31's. As well you could consult the tire manufacturers specifications for their installed height (typically very accurate)

Most are listed here www.tirerack.com

XOC lists my tires at 31.61
YOKO lists them at 31.8



Edited to add:

Quick-draw Ian beat me to it while I was posting the answer.

Thanks guys. Don't feel bad Pacopico you still did good.