315/40 R21 - Best allround tyres 2025 - market overview, tests, reviews

315/40 R21 doesn't belong to the most popular dimensions for allround tyres - there are 0 tyre models available, which can be compared to 155/60 R15, 170/60 R17, 160/60 R14. Let's break down the sizing - 40 is height of the tyre, which is calculated as 40% of the tyre width (315mm), which means the sidewall height has 126 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 2467.41 mm, which is very similar to 275/55 R19(2466.46 mm), 285/40 R22(2471.81 mm), 275/50 R20(2459.87 mm), 255/55 R20(2477.15 mm), 275/65 R17(2479.66 mm), 285/45 R21(2481.54 mm), 275/45 R21(2453.27 mm).