Nokian Powerproof is a summer tyre made in total of 53 sizes, ranging from R17 to R17 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 225/40 R18 is 20mm wider than the narrowest dimension (205) and 50mm narrower than the widest one (275). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (225mm), which results in 90mm sidewall height. In 225/40 R18, there is only one possible speed index for Nokian Powerproof - "Y", which is good for speeds up to 300 km/h. In 225/40 R18, Powerproof usually competes against Roadhawk, which is a tyre from Firestone with a rating of 57%, compared to 54% of the Nokian in question. Latest test in 225/40 R18 was held by Gute-Fahrt in 2019, where Powerproof received rating "Very good -" and finished on the 4. place. It was tested on a .
