305/55R20 tire size
A 305/55R20 tire is 33.2 inches tall and 12.0 inches wide. Here are its full dimensions, what the numbers mean, and the sizes you can swap it for.
- Overall diameter
- 33.21″ (844 mm)
- Section width
- 12.01″ (305 mm)
- Sidewall height
- 6.60″ (168 mm)
- Wheel diameter
- 20″
- Circumference
- 104.3″
- Revolutions per mile
- 607
What 305/55R20 means
- 305: the tire is 305 mm (12.0 in) wide from sidewall to sidewall.
- 55: the sidewall is 55% of the width, 167.8 mm (6.60 in) tall.
- R: radial construction, used by almost every modern tire.
- 20: it fits a 20-inch wheel.
Overall diameter = 20 + 2 × 6.60 = 33.21 inches.
Sizes equivalent to 305/55R20
These sizes are within 3% of the overall diameter, the usual limit for swapping without speedometer problems.
| Size | Diameter | Difference | Speedometer at 60 mph |
|---|---|---|---|
| 285/50R22 | 33.2″ | +0.0% | 60.0 mph actual |
| 315/45R22 | 33.2″ | -0.1% | 59.9 mph actual |
| 285/55R21 | 33.3″ | +0.4% | 60.2 mph actual |
| 315/50R21 | 33.4″ | +0.6% | 60.3 mph actual |
| 305/50R21 | 33.0″ | -0.6% | 59.6 mph actual |
| 285/60R20 | 33.5″ | +0.8% | 60.5 mph actual |
| 325/45R22 | 33.5″ | +0.9% | 60.6 mph actual |
| 305/45R22 | 32.8″ | -1.2% | 59.3 mph actual |
| 295/50R22 | 33.6″ | +1.2% | 60.7 mph actual |
| 325/50R20 | 32.8″ | -1.2% | 59.3 mph actual |
See every common size side by side in the tire size chart.
Questions
What is 305/55R20 in inches?
A 305/55R20 tire is about 33.2 inches tall (844 mm) and 12.0 inches wide, on a 20-inch wheel. In flotation sizing that's roughly 33.2x12.0R20.
How tall is a 305/55R20 tire?
The overall diameter is 33.21 inches: the 20-inch wheel plus two 6.60-inch sidewalls. Actual tires vary by a few tenths of an inch between brands and models.
How many revolutions per mile does a 305/55R20 make?
About 607 revolutions per mile, from a circumference of 104.3 inches.
