195/55 R20 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 (195mm), which means the sidewall height has 107.25 mm. The wheel diameter is R20, which means it fits to a 20 inch/508mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 225/45 R18(2072.51 mm), 295/30 R18(1992.4 mm), 225/55 R19(2293.68 mm), 295/40 R21(2417.14 mm), 225/70 R16(2266.34 mm), 325/25 R20(2106.44 mm), 235/45 R17(2020.99 mm).