275/25 R21 doesn't belong to the most popular dimensions for winter 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 - 25 is height of the tyre, which is calculated as 25% of the tyre width (275mm), which means the sidewall height has 68.75 mm. The wheel diameter is R21, which means it fits to a 21 inch/533.4mm diameter wheel. The total circumference of the tyre is 2107.69 mm, which is very similar to 235/40 R19
(2106.75 mm), 325/25 R20
(2106.44 mm), 200/60 R17
(2110.52 mm), 215/50 R18
(2111.78 mm), 235/35 R20
(2112.72 mm), 265/40 R18
(2102.35 mm), 175/75 R16
(2101.41 mm).
