Hankook Winter I-Cept iOn X is a winter tyre made in total of 23 sizes, ranging from R18 to R18 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. This tyre profile of 55 means the sidewall height of the tyre is 55% of the tyre width (235mm), which results in 129.25mm sidewall height. In 235/55 R20, there is only one possible speed index for Hankook Winter I-Cept iOn X - "V", which is good for speeds up to 240 km/h.