255/45 R15 doesn't belong to the most popular dimensions for summer 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 - 45 is height of the tyre, which is calculated as 45% of the tyre width (255mm), which means the sidewall height has 114.75 mm. The wheel diameter is R15, which means it fits to a 15 inch/381mm diameter wheel. The total circumference of the tyre is 1917.94 mm, which is very similar to 185/55 R16(1916.06 mm), 205/50 R16(1920.77 mm), 195/65 R14(1913.54 mm), 175/65 R15(1911.66 mm), 215/35 R18(1909.15 mm), 205/55 R15(1905.38 mm), 185/70 R14(1930.82 mm).