Bridgestone Blizzak 6 is a winter tyre made in total of 79 sizes, ranging from R16 to R16 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 255/40 R20 is 50mm wider than the narrowest dimension (205) 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 Bridgestone Blizzak 6 - "W", which is good for speeds up to 270 km/h. In 255/40 R20, Blizzak 6 usually competes against Eurowinter Hs02 Pro, which is a tyre from Falken with a rating of 54%, compared to 87% of the Bridgestone in question.