GarageCalc What 285/30R19 means
285 is the section width in millimeters (11.2 in). 30 is the aspect ratio: the sidewall is 30 percent of the width, so 285 × 0.30 = 86 mm (3.4 in). R is radial construction, and 19 is the wheel diameter in inches (483 mm). Stack two sidewalls on the wheel and you get the overall diameter: 483 + 2 × 86 = 654 mm, or 25.7 in.
A full marking adds a load index and speed rating after the size, for example 285/30R19 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 285/30R19
Going up one wheel size, the closest match is 275/30R20 at +3.0% diameter with a 83 mm sidewall instead of 86 mm. Going down one size, 285/35R18 is +0.5% with a taller 100 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 285/30R19 tire?
25.7 inches (654 mm) in overall diameter: the 19-inch wheel (483 mm) plus two 86 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 285/30R19 in inches?
25.7 x 11.2 R19: 25.7 inches tall, 11.2 inches wide, on a 19-inch wheel. The sidewall is 3.4 inches and the circumference is 80.8 inches, so the tire turns 784 times per mile.
What tire sizes are equivalent to 285/30R19?
Within 3 percent of the same diameter on the same 19-inch wheel: 275/30R19 (-0.9%), 295/30R19 (+0.9%), 265/30R19 (-1.8%); on a 20-inch wheel: 275/30R20 (+3.0%); on an 18-inch wheel: 285/35R18 (+0.5%), 275/35R18 (-0.6%). The percentage is the diameter change, which is also your speedometer error.
Can I use 295/30R19 instead of 285/30R19?
Dimensionally yes: 295/30R19 is 0.9% taller (+6 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 59.5 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.