GarageCalc What 185/70R13 means
185 is the section width in millimeters (7.3 in). 70 is the aspect ratio: the sidewall is 70 percent of the width, so 185 × 0.70 = 130 mm (5.1 in). R is radial construction, and 13 is the wheel diameter in inches (330 mm). Stack two sidewalls on the wheel and you get the overall diameter: 330 + 2 × 130 = 589 mm, or 23.2 in.
A full marking adds a load index and speed rating after the size, for example 185/70R13 91V. Those two codes set how much weight and speed the tire is certified for; look them up in the load index chart and the speed rating chart.
Plus and minus sizing from 185/70R13
Going up one wheel size, the closest match is 195/60R14 at +0.1% diameter with a 117 mm sidewall instead of 130 mm. No common 12-inch size stays within 3 percent either. Anything inside 3 percent keeps the speedometer, ABS and gearing effectively stock; the comparison calculator shows the full speedometer table for any pair.
Frequently asked questions
How tall is a 185/70R13 tire?
23.2 inches (589 mm) in overall diameter: the 13-inch wheel (330 mm) plus two 130 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 185/70R13 in inches?
23.2 x 7.3 R13: 23.2 inches tall, 7.3 inches wide, on a 13-inch wheel. The sidewall is 5.1 inches and the circumference is 72.9 inches, so the tire turns 869 times per mile.
What tire sizes are equivalent to 185/70R13?
Within 3 percent of the same diameter on the same 13-inch wheel: 165/80R13 (+0.8%), 175/70R13 (-2.4%); on a 14-inch wheel: 195/60R14 (+0.1%), 165/70R14 (-0.4%). The percentage is the diameter change, which is also your speedometer error.