Semperit Speed-Life 3 is a summer tyre made in total of 112 sizes, ranging from R15 to R15 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 235/45 R18 is 70mm wider than the narrowest dimension (165) and 60mm narrower than the widest one (295). This tyre profile of 45 means the sidewall height of the tyre is 45% of the tyre width (235mm), which results in 105.75mm sidewall height. In 235/45 R18, there is only one possible speed index for Semperit Speed-Life 3 - "Y", which is good for speeds up to 300 km/h. In 235/45 R18, Speed-Life 3 usually competes against Advantage, which is a tyre from BFGoodrich with a rating of 76%, compared to 65% of the Semperit in question.