Continental CrossContact ATR is a winter tyre made in total of 52 sizes, ranging from R15 to R15 - this particular dimension is R15, which means it fits to a 15 inch/381mm diameter wheel. 255/70 R15 is 50mm wider than the narrowest dimension (205) and 20mm narrower than the widest one (275). This tyre profile of 70 means the sidewall height of the tyre is 70% of the tyre width (255mm), which results in 178.5mm sidewall height. In 255/70 R15, there is only one possible speed index for Continental CrossContact ATR - "T", which is good for speeds up to 190 km/h.