Pirelli WINTER SOTTOZERO Serie III is a winter tyre made in total of 228 sizes, ranging from R16 to R16 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 225/50 R18 is 20mm wider than the narrowest dimension (205) and 130mm narrower than the widest one (355). This tyre profile of 50 means the sidewall height of the tyre is 50% of the tyre width (225mm), which results in 112.5mm sidewall height. In 225/50 R18, there is only one possible speed index for Pirelli WINTER SOTTOZERO Serie III - "H", which is good for speeds up to 210 km/h. In 225/50 R18, WINTER SOTTOZERO Serie III usually competes against SP Sport MAXX RT2, which is a tyre from Dunlop with a rating of 72%, compared to 0% of the Pirelli in question.