225/55 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 (225mm), which means the sidewall height has 123.75 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 215/40 R18(1976.69 mm), 275/50 R20(2459.87 mm), 215/55 R18(2179.32 mm), 285/30 R20(2133.14 mm), 215/75 R15(2210.11 mm), 285/40 R20(2312.21 mm), 225/40 R19(2081.62 mm). You can find 225/55 R18 on 24 car models - mainly Peugeot, CITROËN, Jeep, Mitsubishi, Audi.