GarageCalc What 235/50R18 means
235 is the section width in millimeters (9.3 in). 50 is the aspect ratio: the sidewall is 50 percent of the width, so 235 × 0.50 = 118 mm (4.6 in). R is radial construction, and 18 is the wheel diameter in inches (457 mm). Stack two sidewalls on the wheel and you get the overall diameter: 457 + 2 × 118 = 692 mm, or 27.3 in.
A full marking adds a load index and speed rating after the size, for example 235/50R18 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 235/50R18
Going up one wheel size, the closest match is 235/45R19 at +0.3% diameter with a 106 mm sidewall instead of 118 mm. Going down one size, 235/55R17 is -0.3% with a taller 129 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 235/50R18
Typical factory fitments include Ford Mustang EcoBoost and V6 (2015-2023). Tire size changes with trim and wheel option, so confirm on the door-jamb placard before buying.
Frequently asked questions
How tall is a 235/50R18 tire?
27.3 inches (692 mm) in overall diameter: the 18-inch wheel (457 mm) plus two 118 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 235/50R18 in inches?
27.3 x 9.3 R18: 27.3 inches tall, 9.3 inches wide, on an 18-inch wheel. The sidewall is 4.6 inches and the circumference is 85.6 inches, so the tire turns 740 times per mile.
What tire sizes are equivalent to 235/50R18?
Within 3 percent of the same diameter on the same 18-inch wheel: 215/55R18 (+0.2%), 255/45R18 (-0.8%), 225/50R18 (-1.4%); on a 19-inch wheel: 235/45R19 (+0.3%), 255/40R19 (-0.8%); on a 17-inch wheel: 235/55R17 (-0.3%), 215/60R17 (-0.3%). The percentage is the diameter change, which is also your speedometer error.
Can I use 245/50R18 instead of 235/50R18?
Dimensionally yes: 245/50R18 is 1.4% taller (+10 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 59.1 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 245 mm.