215/45 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 - 45 is height of the tyre, which is calculated as 45% of the tyre width (215mm), which means the sidewall height has 96.75 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 155/65 R13
(1670.38 mm), 245/35 R18
(1975.12 mm), 160/60 R18
(2039.52 mm), 245/40 R21
(2291.48 mm), 165/70 R14
(1842.86 mm), 245/55 R17
(2203.2 mm), 175/65 R14
(1831.86 mm).
