215/55 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 (215mm), which means the sidewall height has 118.25 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 275/70 R16(2486.26 mm), 215/70 R15(2142.57 mm), 285/35 R21(2302.47 mm), 225/35 R20(2090.73 mm), 285/50 R20(2491.28 mm), 225/50 R18(2143.19 mm), 295/35 R19(2164.87 mm). You can find 215/55 R18 on 16 car models - mainly Mazda, Nissan, Dodge, DS Automobiles, Chrysler.