275/30 R20 doesn't belong to the most popular dimensions for allround tyres - there are 0 tyre models available, which can be compared to
155/60 R15,
170/60 R17,
160/60 R14. Let's break down the sizing - 30 is height of the tyre, which is calculated as 30% of the tyre width (275mm), which means the sidewall height has 82.5 mm. The wheel diameter is R20, which means it fits to a 20 inch/508mm diameter wheel. The total circumference of the tyre is 2114.29 mm, which is very similar to 205/65 R16
(2113.98 mm), 235/35 R20
(2112.72 mm), 215/50 R18
(2111.78 mm), 200/60 R17
(2110.52 mm), 275/35 R19
(2120.89 mm), 235/40 R19
(2106.75 mm), 325/25 R20
(2106.44 mm). There are multiple speed indexes available for allround tyres in 275/30 R20: V
(240km/h), Y
(300km/h). The same goes for weight indexes: 97.