265/60 R20 doesn't belong to the most popular dimensions for tyres - there are tyre models available, which can be compared to
325/30 R21,
155/60 R15,
155/65 R13. Let's break down the sizing - 60 is height of the tyre, which is calculated as 60% of the tyre width (265mm), which means the sidewall height has 159 mm. The wheel diameter is R20, which means it fits to a 20 inch/508mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 275/70 R16
(2486.26 mm), 215/70 R15
(2142.57 mm), 285/35 R21
(2302.47 mm), 225/35 R20
(2090.73 mm), 285/50 R20
(2491.28 mm), 225/50 R18
(2143.19 mm), 295/35 R19
(2164.87 mm).