185/70 R13 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 - 70 is height of the tyre, which is calculated as 70% of the tyre width (185mm), which means the sidewall height has 129.5 mm. The wheel diameter is R13, which means it fits to a 13 inch/330.2mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 225/70 R15(2186.55 mm), 315/40 R21(2467.41 mm), 235/40 R19(2106.75 mm), 235/55 R17(2168.64 mm), 235/65 R17(2316.3 mm), 155/70 R19(2197.86 mm), 245/35 R20(2134.71 mm).