GarageCalc What 255/60R17 means
255 is the section width in millimeters (10.0 in). 60 is the aspect ratio: the sidewall is 60 percent of the width, so 255 × 0.60 = 153 mm (6.0 in). R is radial construction, and 17 is the wheel diameter in inches (432 mm). Stack two sidewalls on the wheel and you get the overall diameter: 432 + 2 × 153 = 738 mm, or 29.0 in.
A full marking adds a load index and speed rating after the size, for example 255/60R17 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 255/60R17
Going up one wheel size, the closest match is 255/55R18 at -0.0% diameter with a 140 mm sidewall instead of 153 mm. Going down one size, 255/65R16 is +0.0% with a taller 166 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 255/60R17 tire?
29.0 inches (738 mm) in overall diameter: the 17-inch wheel (432 mm) plus two 153 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 255/60R17 in inches?
29.0 x 10.0 R17: 29.0 inches tall, 10.0 inches wide, on a 17-inch wheel. The sidewall is 6.0 inches and the circumference is 91.3 inches, so the tire turns 694 times per mile.
What tire sizes are equivalent to 255/60R17?
Within 3 percent of the same diameter on the same 17-inch wheel: 235/65R17 (-0.1%), 245/65R17 (+1.7%); on an 18-inch wheel: 255/55R18 (-0.0%), 235/60R18 (+0.2%); on a 16-inch wheel: 255/65R16 (+0.0%), 235/70R16 (-0.3%). The percentage is the diameter change, which is also your speedometer error.