255/50 R17 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 - 50 is height of the tyre, which is calculated as 50% of the tyre width (255mm), which means the sidewall height has 127.5 mm. The wheel diameter is R17, which means it fits to a 17 inch/431.8mm diameter wheel. The total circumference of the tyre is 2157.65 mm, which is very similar to 255/45 R18(2157.33 mm), 255/40 R19(2157.02 mm), 255/35 R20(2156.7 mm), 215/65 R16(2154.82 mm), 235/60 R16(2162.67 mm), 225/45 R19(2152.31 mm), 295/30 R20(2151.99 mm).