255/65 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 - 65 is height of the tyre, which is calculated as 65% of the tyre width (255mm), which means the sidewall height has 165.75 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 225/70 R15
(2186.55 mm), 315/40 R21
(2467.41 mm), 235/40 R19
(2106.75 mm), 235/55 R17
(2168.64 mm), 235/65 R17
(2316.3 mm), 155/70 R19
(2197.86 mm), 245/35 R20
(2134.71 mm).
