GT Radial Champiro WinterPro 2 is a winter tyre made in total of 43 sizes, ranging from R13 to R13 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/40 R18 is 100mm wider than the narrowest dimension (155) and -10mm narrower than the widest one (245). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (255mm), which results in 102mm sidewall height. In 255/40 R18, Radial Champiro WinterPro 2 usually competes against WinTech, which is a tyre from Viking with a rating of 58%, compared to 60% of the GT in question.