I know that standard tires, for example (31x10.50) is actually about 30.5" for most tires.
Are metric tires the same way? For example a 265/75/15= 30.6x10.4
Is this tire really 30.6" or is it actually around 30?

 

It's around 30.6" tall. They all vary slightly. Some 31X10.50 may be a little over 31" tall.

 

On tirerack all of the 31" tires say their actual size is around 30.5.. some as high as 30.8" and 30" tires say they around 29.3...

 

Yes, there is some slight variance between brands.

 

Check the MFG website, they list all of the data; actual height, section width, measuring rim used to determine....etc,etc,etc

 

That's why TireRack shows the specific rim width that the tire measurements are taken on. Rim width will slightly effect/change both tire width and height. Narrow rim (minimum width in the range stated) will make a tire slightly taller and narrower, wide rim (max width in the range stated) will make a tire slightly shorter and wider.

 

Okay so my main question is... If I buy a 31x10.50" and a 265/75 from the same brand.. Which will be larger?

 

Only the tape measure will tell.

 

I understand better now! Looked at the measured rim width and now I see what you are talking about. They will be relatively the same, the rim may change the height but only slightly. Thank you for all of your help!

 

An inch is converted to 25.4 mm's.

Metric tires are measured in mm's.

The first number is the sectional width.

The second number is the aspect ratio represented in percentage of sectional width (thickness of the sidewall)

The third is the rim diameter.

One example is 265/75/16

You can convert this to :

265/25.4 * 75% * 2(since theres 2 sections of the sidewall - top and bottom) + 16 = Approx 32.2/10.4/16

 

Also the "standard" sizing you are talking about is actually called "high flotation" as they are constructed to be lighter and perform better during offroad applications such as in sand or mud.

 

265mm/25.4= 10.43"(tread width in inches)
10.43"×1.5= 15.65" (height of sidewalls combined)
15.65"+16"(rim height)= 31.65" diameter

(Section width/25.4)*(aspect ratio*2) + rim

(265/25.4)*(.75*2)+16
(10.43)*(1.5)+16
(15.65)+16
31.65


Extra points awarded for use of parentheses