GarageCalc What 155/70R13 means
155 is the section width in millimeters (6.1 in). 70 is the aspect ratio: the sidewall is 70 percent of the width, so 155 × 0.70 = 109 mm (4.3 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 × 109 = 547 mm, or 21.5 in.
A full marking adds a load index and speed rating after the size, for example 155/70R13 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 155/70R13
Going up one wheel size, the closest match is 165/60R14 at +1.2% diameter with a 99 mm sidewall instead of 109 mm. Going down one size, 155/80R12 is +1.0% with a taller 124 mm sidewall for more comfort and pothole margin. 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 155/70R13 tire?
21.5 inches (547 mm) in overall diameter: the 13-inch wheel (330 mm) plus two 109 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 155/70R13 in inches?
21.5 x 6.1 R13: 21.5 inches tall, 6.1 inches wide, on a 13-inch wheel. The sidewall is 4.3 inches and the circumference is 67.7 inches, so the tire turns 936 times per mile.
What tire sizes are equivalent to 155/70R13?
Within 3 percent of the same diameter on the same 13-inch wheel: 165/65R13 (-0.5%), 175/65R13 (+1.9%), 145/70R13 (-2.6%); on a 14-inch wheel: 165/60R14 (+1.2%), 155/65R14 (+1.8%); on a 12-inch wheel: 155/80R12 (+1.0%), 145/80R12 (-1.9%). The percentage is the diameter change, which is also your speedometer error.
Can I use 165/65R13 instead of 155/70R13?
Dimensionally yes: 165/65R13 is 0.5% shorter (-3 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 60.3 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 165 mm.