GarageCalc What 245/30R22 means
245 is the section width in millimeters (9.6 in). 30 is the aspect ratio: the sidewall is 30 percent of the width, so 245 × 0.30 = 74 mm (2.9 in). R is radial construction, and 22 is the wheel diameter in inches (559 mm). Stack two sidewalls on the wheel and you get the overall diameter: 559 + 2 × 74 = 706 mm, or 27.8 in.
A full marking adds a load index and speed rating after the size, for example 245/30R22 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 245/30R22
No common 23-inch size stays within 3 percent of 27.8 in. Going down one size, 255/35R21 is +0.9% with a taller 89 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 245/30R22 tire?
27.8 inches (706 mm) in overall diameter: the 22-inch wheel (559 mm) plus two 74 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 245/30R22 in inches?
27.8 x 9.6 R22: 27.8 inches tall, 9.6 inches wide, on a 22-inch wheel. The sidewall is 2.9 inches and the circumference is 87.3 inches, so the tire turns 726 times per mile.
What tire sizes are equivalent to 245/30R22?
Within 3 percent of the same diameter on the same 22-inch wheel: 255/30R22 (+0.9%); on a 21-inch wheel: 255/35R21 (+0.9%), 265/35R21 (+1.9%). The percentage is the diameter change, which is also your speedometer error.
Can I use 255/30R22 instead of 245/30R22?
Dimensionally yes: 255/30R22 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 255 mm.