How to read tire sizes
 

how exactly do you read a tire size what does each number mena like in 325/65/18 i know the 18 is rim size, but what is the other and how do you knwo from that measurement how many inches the tires are.

thanks

First number is section width in milimeters. Second number is percentage of sidewall height to section width.

So, 325mm wide / 25.4 mm per inch ~ 12.8" wide
65% of 325mm = ~8.3" of rubber between the rim and road

There are two pieces of rubber on a diameter of a wheel so 2*8.3" + 18" wheel = 34.6" diameter tires, or what most people call a 35" tire.

Tirerack
s Tire Tech Page has a little more details. Remember, these are theoretical sizes as each tire brand/model will be slightly different.

Thanks a bunch

Try this link for tire size comparisons