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 225/50 R17(2063.4 mm), 295/30 R22(2311.58 mm), 225/60 R17(2204.77 mm), 305/30 R19(2091.04 mm), 235/35 R19(2032.92 mm), 235/45 R20(2260.38 mm), 235/60 R16(2162.67 mm).