255/40 R18 doesn't belong to the most popular dimensions for tyres - there are tyre models available, which can be compared to
325/30 R21,
155/60 R15,
155/65 R13. Let's break down the sizing - 40 is height of the tyre, which is calculated as 40% of the tyre width (255mm), which means the sidewall height has 102 mm. The wheel diameter is R18, which means it fits to a 18 inch/457.2mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 245/65 R17
(2357.14 mm), 175/70 R14
(1886.84 mm), 255/35 R20
(2156.7 mm), 185/55 R15
(1836.26 mm), 255/45 R20
(2316.92 mm), 185/75 R14
(1988.94 mm), 255/65 R16
(2318.18 mm). You can find 255/40 R18 on 14 car models - mainly .
