Michelin Pilot Sport 4 is a summer tyre made in total of 159 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 50mm wider than the narrowest dimension (205) and 70mm narrower than the widest one (325). 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 are 2 possible speed indexes for Michelin Pilot Sport 4 - "W","Y", which are good for speeds up to 270, 300 km/h. In 255/45 R18, Pilot Sport 4 usually competes against Eagle F1 Asymmetric 5, which is a tyre from GoodYear with a rating of 90%, compared to 88% of the Michelin in question.