2nd Godfather / Administrator
2005 Granite Xterra Off-Road
Join Date: Jan 2006
So that people can see how the tire size is calculated.
The 33x11.50x16 is actually very easy to unserstand. That would be a 33" diameter tire, 11.50" wide and fit a 16" wheel.
285/75R16 is confusing as all get out in the US world of non metric standards.
285 is the width of the tire in mm
75 is the aspect ratio of sidewall height vs width
16 is the wheel size in inches.
So....to convert 285/75R16 into the inches (which is what most people look for).
To find the width of the tire in inches.
25.4 is how many mm per inch.
To find the height of the tire in inches.
The height of the sidewall is 213.75mm Since we want to find the height, we need to times it by 2 (since there are two sidewalls in the diameter of the tire)
Now we conver this to inches.
Now we need to add the wheel size to complete the height.
So...a 285/75R16 tire is a 32.8x11.2x16 or very close to a 33x11.5x16 which is usually what everyone refers to them as.
I hope that makes some sense. If you do a search there are calculators to do the conversions for you. I find it easier to understand if I know how it's calculated. You now also probably know more about tire sizes than the folks selling them at the local tire stores.