Pirelli Cinturato P7 is a summer tyre made in total of 205 sizes, ranging from R16 to R16 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/45 R18 is 60mm wider than the narrowest dimension (195) and -60mm narrower than the widest one (195). This tyre profile of 45 means the sidewall height of the tyre is 45% of the tyre width (255mm), which results in 114.75mm sidewall height. In 255/45 R18, there is only one possible speed index for Pirelli Cinturato P7 - "W", which is good for speeds up to 270 km/h.