Nokian WR A4 is a winter tyre made in total of 59 sizes, ranging from R16 to R16 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/45 R18 is 50mm wider than the narrowest dimension (205) and -10mm narrower than the widest one (245). This tyre profile of 45 means the sidewall height of the tyre is 45% of the tyre width (255mm), which results in 114.75mm sidewall height. In
255/45 R18, WR A4 usually competes against
ContiWinterContact TS 850P, which is a tyre from
Continental with a rating of 0%, compared to 0% of the
Nokian in question.