195/50 R20 doesn't belong to the most popular dimensions for summer tyres - there are 2 tyre models available, which can be compared to 155/60 R15, 170/60 R17, 160/60 R14. Let's break down the sizing - 50 is height of the tyre, which is calculated as 50% of the tyre width (195mm), which means the sidewall height has 97.5 mm. The wheel diameter is R20, which means it fits to a 20 inch/508mm diameter wheel. The total circumference of the tyre is 2208.54 mm, which is very similar to 245/45 R19(2208.85 mm), 275/40 R19(2207.28 mm), 215/75 R15(2210.11 mm), 245/50 R18(2206.03 mm), 245/40 R20(2211.68 mm), 225/60 R17(2204.77 mm), 285/30 R21(2212.94 mm). There are multiple speed indexes available for summer tyres in 195/50 R20: T(190km/h), W(270km/h). The same goes for weight indexes: 93.