305/30 R21 - Best tyres 2025 - market overview, tests, reviews

305/30 R21 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 - 30 is height of the tyre, which is calculated as 30% of the tyre width (305mm), which means the sidewall height has 91.5 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 195/65 R15(1993.34 mm), 265/40 R20(2261.95 mm), 200/60 R17(2110.52 mm), 265/60 R18(2435.36 mm), 205/55 R15(1905.38 mm), 275/30 R20(2114.29 mm), 205/70 R15(2098.58 mm).