Vredestein ULTRAC is a summer tyre made in total of 49 sizes, ranging from R15 to R15 - this particular dimension is R18, which means it fits to a 18 inch/457.2mm diameter wheel. 255/35 R18 is 80mm wider than the narrowest dimension (175) and 40mm narrower than the widest one (295). This tyre profile of 35 means the sidewall height of the tyre is 35% of the tyre width (255mm), which results in 89.25mm sidewall height. In 255/35 R18, there is only one possible speed index for Vredestein ULTRAC - "Y", which is good for speeds up to 300 km/h.