235/55 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 - 55 is height of the tyre, which is calculated as 55% of the tyre width (235mm), which means the sidewall height has 129.25 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 215/60 R17(2167.07 mm), 285/35 R18(2063.08 mm), 215/80 R15(2277.65 mm), 285/45 R19(2321.95 mm), 225/45 R18(2072.51 mm), 295/30 R19(2072.19 mm), 225/55 R19(2293.68 mm). You can find 235/55 R18 on 20 car models - mainly Audi, Lexus, SsangYong, Volvo, Cadillac.