What size tire is a 305?
R20 tire size explanation in this case, the tire’s width is 305 mm (12. The aspect ratio is expressed as a percentage of the tire’s height to its width. A 55-aspect ratio means that the tire’s height is 55% of its width (in this case it is 167. These numbers show the aspect ratio, which is the tire sidewall height in percentage to width of the tire. The width of sidewall is directly proportional to the aspect ratio, a 70 aspect ratio means the sidewall height is 70% of 265mm while 65 aspect ratio means it is 65% of 265mm.