255/55R18 tire size
A 255/55R18 tire is 29.0 inches tall and 10.0 inches wide. Here are its full dimensions, what the numbers mean, and the sizes you can swap it for.
- Overall diameter
- 29.04″ (738 mm)
- Section width
- 10.04″ (255 mm)
- Sidewall height
- 5.52″ (140 mm)
- Wheel diameter
- 18″
- Circumference
- 91.2″
- Revolutions per mile
- 694
What 255/55R18 means
- 255: the tire is 255 mm (10.0 in) wide from sidewall to sidewall.
- 55: the sidewall is 55% of the width, 140.3 mm (5.52 in) tall.
- R: radial construction, used by almost every modern tire.
- 18: it fits a 18-inch wheel.
Overall diameter = 18 + 2 × 5.52 = 29.04 inches.
Sizes equivalent to 255/55R18
These sizes are within 3% of the overall diameter, the usual limit for swapping without speedometer problems.
| Size | Diameter | Difference | Speedometer at 60 mph |
|---|---|---|---|
| 255/50R19 | 29.0″ | -0.0% | 60.0 mph actual |
| 255/45R20 | 29.0″ | -0.0% | 60.0 mph actual |
| 235/60R18 | 29.1″ | +0.2% | 60.1 mph actual |
| 235/55R19 | 29.2″ | +0.5% | 60.3 mph actual |
| 235/50R20 | 29.3″ | +0.7% | 60.4 mph actual |
| 275/50R18 | 28.8″ | -0.7% | 59.6 mph actual |
| 275/45R19 | 28.7″ | -1.0% | 59.4 mph actual |
| 265/45R20 | 29.4″ | +1.2% | 60.7 mph actual |
| 245/45R20 | 28.7″ | -1.2% | 59.3 mph actual |
| 275/40R20 | 28.7″ | -1.3% | 59.2 mph actual |
Going a size taller? 235/60R18 is 29.1″ tall, 0.2% more than 255/55R18. Compare any two sizes in the tire size calculator.
See every common size side by side in the tire size chart.
Questions
What is 255/55R18 in inches?
A 255/55R18 tire is about 29.0 inches tall (738 mm) and 10.0 inches wide, on a 18-inch wheel. In flotation sizing that's roughly 29.0x10.0R18.
How tall is a 255/55R18 tire?
The overall diameter is 29.04 inches: the 18-inch wheel plus two 5.52-inch sidewalls. Actual tires vary by a few tenths of an inch between brands and models.
How many revolutions per mile does a 255/55R18 make?
About 694 revolutions per mile, from a circumference of 91.2 inches.
