Hankook ION Evo is a summer tyre made in total of 64 sizes, ranging from R17 to R17 - this particular dimension is R21, which means it fits to a 21 inch/533.4mm diameter wheel. 245/40 R21 is 30mm wider than the narrowest dimension (215) and 40mm narrower than the widest one (285). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (245mm), which results in 98mm sidewall height. In 245/40 R21, there is only one possible speed index for Hankook ION Evo - "Y", which is good for speeds up to 300 km/h. In 245/40 R21, 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.