Size 31x10.5 R15
On the sidewall of the tyre there is a series of characters which are the tyre size, e.g. 31x10.5 R15, where the first number is the section width measured between the tyre sidewalls in millimetres. The second number in the tyre size is the profile height, which is a percentage of the tyre width, e.g. 55 is 55% of 205, or 112.75 mm. "R" indicates the type of tyre (R - radial, D - diagonal). The last number indicates the width of the rim in inches. Knowing your tyre size is essential when purchasing.