Goodyear UltraGrip is a winter tyre made in total of 6 sizes, ranging from R17 to R17 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/55 R18 is 20mm wider than the narrowest dimension (235) and 0mm narrower than the widest one (255). This tyre profile of 55 means the sidewall height of the tyre is 55% of the tyre width (255mm), which results in 140.25mm sidewall height. In 255/55 R18, there is only one possible speed index for Goodyear UltraGrip - "H", which is good for speeds up to 210 km/h. In 255/55 R18, UltraGrip usually competes against SportContact 5 SUV, which is a tyre from Continental with a rating of 0%, compared to 0% of the Goodyear in question.