285/40 R21 - Best tyres 2025 - market overview, tests, reviews

285/40 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 - 40 is height of the tyre, which is calculated as 40% of the tyre width (285mm), which means the sidewall height has 114 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 245/65 R17(2357.14 mm), 175/70 R14(1886.84 mm), 255/35 R20(2156.7 mm), 185/55 R15(1836.26 mm), 255/45 R19(2237.13 mm), 185/75 R14(1988.94 mm), 255/60 R18(2397.66 mm).