Nexen N fera Sport is a summer tyre made in total of 24 sizes, ranging from R16 to R16 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/45 R18 is 50mm wider than the narrowest dimension (205) and -10mm narrower than the widest one (245). This tyre profile of 45 means the sidewall height of the tyre is 45% of the tyre width (255mm), which results in 114.75mm sidewall height. In 255/45 R18, there is only one possible speed index for Nexen N fera Sport - "Y", which is good for speeds up to 300 km/h. In 255/45 R18, N fera Sport usually competes against N Blue 4 Season 2, which is a tyre from Nexen with a rating of 62%, compared to 59% of the Nexen in question.