Firestone Roadhawk 2 is a summer tyre made in total of 93 sizes, ranging from R17 to R17 - this particular dimension is R21, which means it fits to a 21 inch/533.4mm diameter wheel. 275/45 R21 is 80mm wider than the narrowest dimension (195) and 20mm narrower than the widest one (295). This tyre profile of 45 means the sidewall height of the tyre is 45% of the tyre width (275mm), which results in 123.75mm sidewall height. In 275/45 R21, there is only one possible speed index for Firestone Roadhawk 2 - "Y", which is good for speeds up to 300 km/h. In 275/45 R21, Roadhawk 2 usually competes against Roadhawk, which is a tyre from Firestone with a rating of %, compared to 74% of the Firestone in question.