275/40 R20 doesn't belong to the most popular dimensions for allround tyres - there are 1 tyre models available, which can be compared to 155/60 R15, 170/60 R17, 160/60 R14. Let's break down the sizing - 40 is height of the tyre, which is calculated as 40% of the tyre width (275mm), which means the sidewall height has 110 mm. The wheel diameter is R20, which means it fits to a 20 inch/508mm diameter wheel. The total circumference of the tyre is 2287.08 mm, which is very similar to 325/30 R21(2288.34 mm), 245/50 R19(2285.82 mm), 315/35 R20(2288.65 mm), 245/45 R20(2288.65 mm), 225/60 R18(2284.57 mm), 215/75 R16(2289.91 mm), 245/40 R21(2291.48 mm). There are multiple speed indexes available for allround tyres in 275/40 R20: H(210km/h), V(240km/h), W(270km/h), Y(300km/h). The same goes for weight indexes: 106. You can find 275/40 R20 on 8 car models - mainly BMW, Dodge, Bentley, Land Rover, Porsche.