Uniroyal RainSport 5 is a summer tyre made in total of 121 sizes, ranging from R15 to R15 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 245/40 R18 is 60mm wider than the narrowest dimension (185) and 50mm narrower than the widest one (295). 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 R18, there is only one possible speed index for Uniroyal RainSport 5 - "Y", which is good for speeds up to 300 km/h. In 245/40 R18, RainSport 5 usually competes against RainSport 3, which is a tyre from Uniroyal with a rating of 78%, compared to 76% of the Uniroyal in question.