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
Similar diameter does not establish interchangeability. Follow the vehicle manufacturer's approved sizes; see Michelin's tire-size guidance.
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. The 3 percent cutoff is a comparison filter, not a fitment approval. Use vehicle-approved sizes and check rim width, load and speed ratings, and clearances. 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. Actual dimensions depend on the tire model, tread depth, pressure and load; check the tire manufacturer specifications.
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?
Nominal size comparison only: 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. This does not confirm fitment. Check approved rim widths, load and speed ratings, and vehicle clearances. The nominal extra width adds about 0.20 in of clearance on each side of the tire and a rim width that suits 165 mm.