Hankook ION Evo is a summer tyre made in total of 64 sizes, ranging from R13 to R13 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 255/40 R20 is 40mm wider than the narrowest dimension (215) and 30mm narrower than the widest one (285). 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 R20, there is only one possible speed index for Hankook ION Evo - "W", which is good for speeds up to 270 km/h. In 255/40 R20, ION Evo usually competes against P ZERO PZ4, which is a tyre from Pirelli with a rating of 89%, compared to 90% of the Hankook in question.