Firestone Winterhawk 4 is a winter tyre made in total of 100 sizes, ranging from R14 to R14 - this particular dimension is R15, which means it fits to a 15 inch/381mm diameter wheel. 195/50 R15 is 40mm wider than the narrowest dimension (155) and 80mm narrower than the widest one (275). This tyre profile of 50 means the sidewall height of the tyre is 50% of the tyre width (195mm), which results in 97.5mm sidewall height. In 195/50 R15, there is only one possible speed index for Firestone Winterhawk 4 - "H", which is good for speeds up to 210 km/h. In 195/50 R15, Winterhawk 4 usually competes against WR D4, which is a tyre from Nokian with a rating of 54%, compared to 69% of the Firestone in question.