155/80 R12 doesn't belong to the most popular dimensions for summer tyres - there are 4 tyre models available, which can be compared to 155/60 R15, 170/60 R17, 160/60 R14. Let's break down the sizing - 80 is height of the tyre, which is calculated as 80% of the tyre width (155mm), which means the sidewall height has 124 mm. The wheel diameter is R12, which means it fits to a 12 inch/304.8mm diameter wheel. The total circumference of the tyre is 1736.67 mm, which is very similar to 165/60 R14(1739.19 mm), 195/45 R15(1748.3 mm), 155/65 R14(1750.18 mm), 175/65 R13(1752.07 mm), 160/60 R14(1720.34 mm), 155/70 R13(1719.08 mm), 185/55 R14(1756.46 mm). There are multiple speed indexes available for summer tyres in 155/80 R12: R(170km/h). The same goes for weight indexes: 88.