GarageCalc What 285/70R17 means
285 is the section width in millimeters (11.2 in). 70 is the aspect ratio: the sidewall is 70 percent of the width, so 285 × 0.70 = 200 mm (7.9 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 × 200 = 831 mm, or 32.7 in.
A full marking adds a load index and speed rating after the size, for example 285/70R17 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 285/70R17
Going up one wheel size, the closest match is 265/70R18 at -0.3% diameter with a 186 mm sidewall instead of 200 mm. Going down one size, 305/70R16 is +0.3% with a taller 214 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.
Which cars come with 285/70R17
Typical factory fitments include Jeep Wrangler JL Rubicon, Jeep Gladiator Rubicon and Ford Bronco Badlands. Tire size changes with trim and wheel option, so confirm on the door-jamb placard before buying.
Frequently asked questions
How tall is a 285/70R17 tire?
32.7 inches (831 mm) in overall diameter: the 17-inch wheel (432 mm) plus two 200 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 285/70R17 in inches?
32.7 x 11.2 R17: 32.7 inches tall, 11.2 inches wide, on a 17-inch wheel. The sidewall is 7.9 inches and the circumference is 102.8 inches, so the tire turns 617 times per mile.
What tire sizes are equivalent to 285/70R17?
Within 3 percent of the same diameter on the same 17-inch wheel: 275/70R17 (-1.7%), 295/70R17 (+1.7%); on an 18-inch wheel: 265/70R18 (-0.3%), 285/65R18 (-0.4%); on a 16-inch wheel: 305/70R16 (+0.3%), 285/75R16 (+0.4%). The percentage is the diameter change, which is also your speedometer error.
Can I use 295/70R17 instead of 285/70R17?
Dimensionally yes: 295/70R17 is 1.7% taller (+14 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 59.0 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 295 mm.