Nokian WR SUV 4 is a winter tyre made in total of 69 sizes, ranging from R16 to R16 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 235/50 R18 is 20mm wider than the narrowest dimension (215) and 80mm narrower than the widest one (315). This tyre profile of 50 means the sidewall height of the tyre is 50% of the tyre width (235mm), which results in 117.5mm sidewall height. In 235/50 R18, there is only one possible speed index for Nokian WR SUV 4 - "V", which is good for speeds up to 240 km/h. In 235/50 R18, WR SUV 4 usually competes against WR SUV 3, which is a tyre from Nokian with a rating of 0%, compared to 26% of the Nokian in question.