Bridgestone Potenza RE050A is a summer tyre made in total of 90 sizes, ranging from R15 to R15 - this particular dimension is R19, which means it fits to a 19 inch/482.6mm diameter wheel. 245/40 R19 is 70mm wider than the narrowest dimension (175) and 60mm narrower than the widest one (305). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (245mm), which results in 98mm sidewall height. In 245/40 R19, there are 2 possible speed indexes for Bridgestone Potenza RE050A - "W","Y", which are good for speeds up to 270, 300 km/h.