Tire size question

[racer_d]

Just to expand on tire reading basics:

225 40 18

225 = section width of the tire, in millimeters

40 = aspect ratio - the percentage of the section width that then defines the sidewall height. In this case, the side wall height is 40% of the tires width (225 x .40 = 90mm)

18 = rim diameter in inches

so.. a 225-40-18 is both narrower (225<245) and "shorter" ( 40% of 225 =90, 40% of 245 = 98) than a 245-40-18.