Cooper Discoverer Winter is a winter tyre made in total of 37 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 60mm narrower than the widest one (295). 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 Cooper Discoverer Winter - "V", which is good for speeds up to 240 km/h. In 235/50 R18, Discoverer Winter usually competes against Wintrac Pro, which is a tyre from Vredestein with a rating of 87%, compared to 79% of the Cooper in question.