195/55 R20 doesn't belong to the most popular dimensions for allround tyres - there are 3 tyre models available, which can be compared to 155/60 R15, 170/60 R17, 160/60 R14. 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 2269.8 mm, which is very similar to 225/70 R16(2266.34 mm), 225/65 R17(2275.46 mm), 215/80 R15(2277.65 mm), 265/40 R20(2261.95 mm), 235/45 R20(2260.38 mm), 275/35 R21(2280.48 mm), 265/35 R21(2258.49 mm). There are multiple speed indexes available for allround tyres in 195/55 R20: H(210km/h). The same goes for weight indexes: 95.