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 165/80 R13
(1866.73 mm), 245/55 R17
(2203.2 mm), 175/65 R15
(1911.66 mm), 255/35 R18
(1997.11 mm), 185/50 R16
(1857.94 mm), 255/45 R18
(2157.33 mm), 185/65 R15
(1952.5 mm). You can find 255/40 R18 on 14 car models - mainly .
