Riken Ultra High Performance 225/40 R18

Riken Ultra High Performance is a tyre made in total of 55 sizes, ranging from R17 to R17 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 225/40 R18 is 20mm wider than the narrowest dimension (205) and -30mm narrower than the widest one (195). This tyre profile of 40 means the sidewall height of the tyre is 40% of the tyre width (225mm), which results in 90mm sidewall height.