Nokian WR A4 is a winter tyre made in total of 59 sizes, ranging from R16 to R16 - this particular dimension is R19, which means it fits to a 19 inch/482.6mm diameter wheel. 255/40 R19 is 50mm wider than the narrowest dimension (205) and -10mm narrower than the widest one (245). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (255mm), which results in 102mm sidewall height. In 255/40 R19, there is only one possible speed index for Nokian WR A4 - "V", which is good for speeds up to 240 km/h. In 255/40 R19, WR A4 usually competes against ContiWinterContact TS 850P, which is a tyre from Continental with a rating of 53%, compared to 0% of the Nokian in question.