Maxtrek TREK M7 is a winter tyre made in total of 3 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 40mm wider than the narrowest dimension (185) and 40mm narrower than the widest one (265). 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 Maxtrek TREK M7 - "T", which is good for speeds up to 190 km/h.