Pirelli P ZERO lx. is a summer tyre made in total of 113 sizes, ranging from R18 to R18 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 255/40 R20 is 30mm wider than the narrowest dimension (225) and 60mm narrower than the widest one (315). 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 R20, there is only one possible speed index for Pirelli P ZERO lx. - "V", which is good for speeds up to 240 km/h. In 255/40 R20, P ZERO lx. usually competes against Pilot Sport 4 S, which is a tyre from Michelin with a rating of 86%, compared to 85% of the Pirelli in question.