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 195/70 R15(2054.6 mm), 265/45 R21(2425 mm), 205/45 R16(1856.37 mm), 265/70 R16(2442.27 mm), 205/55 R19(2224.56 mm), 275/35 R20(2200.69 mm), 215/35 R18(1909.15 mm). You can find 225/55 R18 on 24 car models - mainly Peugeot, CITROËN, Jeep, Mitsubishi, Audi.