Nokian Powerproof SUV is a summer tyre made in total of 29 sizes, ranging from R17 to R17 - this particular dimension is R21, which means it fits to a 21 inch/533.4mm diameter wheel. 255/40 R21 is 20mm wider than the narrowest dimension (235) and 40mm narrower than the widest one (295). 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 R21, Powerproof SUV usually competes against
Dynaxer HP5, which is a tyre from
Kleber with a rating of 60%, compared to 0% of the
Nokian in question.