325/30 R21 doesn't belong to the most popular dimensions for allseason tyres - there are tyre models available, which can be compared to
325/25 R20,
155/60 R15,
155/65 R13. Let's break down the sizing - 30 is height of the tyre, which is calculated as 30% of the tyre width (325mm), which means the sidewall height has 97.5 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 mm, which is very similar to 285/45 R21
(2481.54 mm), 225/50 R17
(2063.4 mm), 295/30 R22
(2311.58 mm), 225/60 R17
(2204.77 mm), 305/30 R19
(2091.04 mm), 235/35 R19
(2032.92 mm), 235/45 R20
(2260.38 mm).
