Nokian WR Snowproof is a winter tyre made in total of 60 sizes, ranging from R14 to R14 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 225/50 R18 is 60mm wider than the narrowest dimension (165) and -10mm narrower than the widest one (215). 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 Nokian WR Snowproof - "H", which is good for speeds up to 210 km/h.
