355/25 R21 doesn't belong to the most popular dimensions for winter 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 - 25 is height of the tyre, which is calculated as 25% of the tyre width (355mm), which means the sidewall height has 88.75 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 2233.36 mm, which is very similar to 285/40 R19
(2232.42 mm), 215/65 R17
(2234.61 mm), 235/65 R16
(2236.5 mm), 255/40 R20
(2236.81 mm), 255/45 R19
(2237.13 mm), 205/55 R19
(2224.56 mm), 235/60 R17
(2242.47 mm). There are multiple speed indexes available for winter tyres in 355/25 R21: W
(270km/h). The same goes for weight indexes: 107.
