Pirelli Cinturato All Season Plus is a allround tyre made in total of 70 sizes, ranging from R14 to R14 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 235/45 R18 is 70mm wider than the narrowest dimension (165) and -40mm narrower than the widest one (195). This tyre profile of 45 means the sidewall height of the tyre is 45% of the tyre width (235mm), which results in 105.75mm sidewall height. In 235/45 R18, there is only one possible speed index for Pirelli Cinturato All Season Plus - "Y", which is good for speeds up to 300 km/h.