Dunlop SP Sport MAXX GT600 is a summer tyre made in total of 15 sizes, ranging from R20 to R20 - this particular dimension is R20, which means it fits to a 20 inch/508mm diameter wheel. 285/35 R20 is 30mm wider than the narrowest dimension (255) and 0mm narrower than the widest one (285). This tyre profile of 35 means the sidewall height of the tyre is 35% of the tyre width (285mm), which results in 99.75mm sidewall height. In 285/35 R20, there is only one possible speed index for Dunlop SP Sport MAXX GT600 - "Y", which is good for speeds up to 300 km/h.