Imperial All Season Driver is a allround tyre made in total of 133 sizes, ranging from R13 to R13 - this particular dimension is R15, which means it fits to a 15 inch/381mm diameter wheel. 185/55 R15 is 40mm wider than the narrowest dimension (145) and 90mm narrower than the widest one (275). This tyre profile of 55 means the sidewall height of the tyre is 55% of the tyre width (185mm), which results in 101.75mm sidewall height. In 185/55 R15, there are 2 possible speed indexes for Imperial All Season Driver - "H","V", which are good for speeds up to 210, 240 km/h.