GarageCalc What 295/55R20 means
295 is the section width in millimeters (11.6 in). 55 is the aspect ratio: the sidewall is 55 percent of the width, so 295 × 0.55 = 162 mm (6.4 in). R is radial construction, and 20 is the wheel diameter in inches (508 mm). Stack two sidewalls on the wheel and you get the overall diameter: 508 + 2 × 162 = 833 mm, or 32.8 in.
A full marking adds a load index and speed rating after the size, for example 295/55R20 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 295/55R20
Going up one wheel size, the closest match is 275/50R21 at -2.9% diameter with a 138 mm sidewall instead of 162 mm. No common 19-inch size stays within 3 percent either. 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 295/55R20 tire?
32.8 inches (833 mm) in overall diameter: the 20-inch wheel (508 mm) plus two 162 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 295/55R20 in inches?
32.8 x 11.6 R20: 32.8 inches tall, 11.6 inches wide, on a 20-inch wheel. The sidewall is 6.4 inches and the circumference is 103.0 inches, so the tire turns 615 times per mile.
What tire sizes are equivalent to 295/55R20?
Within 3 percent of the same diameter on the same 20-inch wheel: 275/60R20 (+0.7%), 285/55R20 (-1.3%), 305/55R20 (+1.3%); on a 21-inch wheel: 275/50R21 (-2.9%). The percentage is the diameter change, which is also your speedometer error.
Can I use 305/55R20 instead of 295/55R20?
Dimensionally yes: 305/55R20 is 1.3% taller (+11 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 59.2 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 305 mm.