255/40 R22 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 (255mm), which means the sidewall height has 102 mm. The wheel diameter is R22, which means it fits to a 22 inch/558.8mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 185/60 R16(1974.18 mm), 255/55 R18(2317.55 mm), 190/55 R17(2013.13 mm), 255/70 R16(2398.29 mm), 195/55 R20(2269.8 mm), 265/35 R20(2178.69 mm), 195/70 R15(2054.6 mm).