Riken Ultra High Performance is a tyre made in total of 55 sizes, ranging from R17 to R17 - this particular dimension is R17, which means it fits to a 17 inch/431.8mm diameter wheel. 225/55 R17 is 20mm wider than the narrowest dimension (205) and -30mm narrower than the widest one (195). This tyre profile of 55 means the sidewall height of the tyre is 55% of the tyre width (225mm), which results in 123.75mm sidewall height. In 225/55 R17, there are 2 possible speed indexes for Riken Ultra High Performance - "Y","W", which are good for speeds up to 300, 270 km/h.