Nokian Powerproof 1 is a summer tyre made in total of 54 sizes, ranging from R17 to R17 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/40 R18 is 50mm wider than the narrowest dimension (205) and 20mm narrower than the widest one (275). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (255mm), which results in 102mm sidewall height. In
255/40 R18, Powerproof 1 usually competes against
Potenza Sport, which is a tyre from
Bridgestone with a rating of 87%, compared to 57% of the
Nokian in question.