Pirelli Scorpion ZERO is a summer tyre made in total of 11 sizes, ranging from R18 to R18 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 285/55 R18 is 50mm wider than the narrowest dimension (235) and -20mm narrower than the widest one (265). This tyre profile of 55 means the sidewall height of the tyre is 55% of the tyre width (285mm), which results in 156.75mm sidewall height. In 285/55 R18, there is only one possible speed index for Pirelli Scorpion ZERO - "V", which is good for speeds up to 240 km/h.