285/50 R20 doesn't belong to the most popular dimensions for winter tyres - there are 6 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 (285mm), which means the sidewall height has 142.5 mm. The wheel diameter is R20, which means it fits to a 20 inch/508mm diameter wheel. The total circumference of the tyre is 2491.28 mm, which is very similar to 275/70 R16(2486.26 mm), 285/45 R21(2481.54 mm), 275/65 R17(2479.66 mm), 255/55 R20(2477.15 mm), 285/40 R22(2471.81 mm), 285/60 R18(2510.76 mm), 315/40 R21(2467.41 mm). There are multiple speed indexes available for winter tyres in 285/50 R20: H(210km/h), R(170km/h), T(190km/h). The same goes for weight indexes: 110, 112, 116.