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 165/65 R15(1870.82 mm), 245/50 R18(2206.03 mm), 175/60 R15(1856.68 mm), 245/75 R16(2431.28 mm), 180/55 R17(1978.58 mm), 255/40 R19(2157.02 mm), 185/60 R15(1894.38 mm).