Pirelli Cinturato P7 C2 is a summer tyre made in total of 84 sizes, ranging from R16 to R16 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 275/40 R18 is 70mm wider than the narrowest dimension (205) and -20mm narrower than the widest one (255). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (275mm), which results in 110mm sidewall height. In 275/40 R18, there is only one possible speed index for Pirelli Cinturato P7 C2 - "Y", which is good for speeds up to 300 km/h.