GarageCalc What 155/65R13 means
155 is the section width in millimeters (6.1 in). 65 is the aspect ratio: the sidewall is 65 percent of the width, so 155 × 0.65 = 101 mm (4.0 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 × 101 = 532 mm, or 20.9 in.
A full marking adds a load index and speed rating after the size, for example 155/65R13 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 155/65R13
No common 14-inch size stays within 3 percent of 20.9 in. Going down one size, 145/80R12 is +1.0% with a taller 116 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 155/65R13 tire?
20.9 inches (532 mm) in overall diameter: the 13-inch wheel (330 mm) plus two 101 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 155/65R13 in inches?
20.9 x 6.1 R13: 20.9 inches tall, 6.1 inches wide, on a 13-inch wheel. The sidewall is 4.0 inches and the circumference is 65.8 inches, so the tire turns 963 times per mile.
What tire sizes are equivalent to 155/65R13?
Within 3 percent of the same diameter on the same 13-inch wheel: 145/70R13 (+0.3%), 165/65R13 (+2.4%), 155/70R13 (+2.9%); on a 12-inch wheel: 145/80R12 (+1.0%), 155/70R12 (-1.9%). The percentage is the diameter change, which is also your speedometer error.
Can I use 165/65R13 instead of 155/65R13?
Dimensionally yes: 165/65R13 is 2.4% taller (+13 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 58.6 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.