Continental Wintercontact Ts860S is a winter tyre made in total of 48 sizes, ranging from R16 to R16 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 255/55 R20 is 60mm wider than the narrowest dimension (195) and -40mm narrower than the widest one (215). This tyre profile of 55 means the sidewall height of the tyre is 55% of the tyre width (255mm), which results in 140.25mm sidewall height. In 255/55 R20, there is only one possible speed index for Continental Wintercontact Ts860S - "H", which is good for speeds up to 210 km/h.