30.6" tall, 9.6" wide, 5.3" sidewall
A 245/55R20 tire is 30.6 inches (778 mm) tall and 9.6 inches wide. The sidewall is 55% of the width, 5.3 inches, on a 20-inch wheel, and the tire turns about 659 times per mile.
In flotation terms that is about 30.6x9.6R20. People often call it a 31-inch tire.
The size most often compared with it is 265/55R20, which is 0.9" taller (+2.8%). At an indicated 60 mph you would be doing 61.7 mph on it.
| Current | New | Difference |
|---|
| Shows | Actual speed |
|---|
Same 20" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 245/55R20 | |
|---|---|---|---|---|---|
| 265/55R20 | 31.5" | 10.4" | 5.7" | +2.8% | |
| 245/60R20 | 31.6" | 9.6" | 5.8" | +3.2% | |
| 255/60R20 | 32.0" | 10.0" | 6.0" | +4.7% | |
| 265/60R20 | 32.5" | 10.4" | 6.3" | +6.2% | |
| 255/65R20 | 33.1" | 10.0" | 6.5" | +8.0% | |
| 265/65R20 | 33.6" | 10.4" | 6.8" | +9.6% |
Sizes within 2% of 30.6" on 18" or 22" wheels.
| Size | Diameter | Width | Sidewall | vs 245/55R20 | |
|---|---|---|---|---|---|
| 245/65R18 | 30.5" | 9.6" | 6.3" | −0.2% | |
| 295/55R18 | 30.8" | 11.6" | 6.4" | +0.5% | |
| 305/35R22 | 30.4" | 12.0" | 4.2" | −0.7% | |
| 285/55R18 | 30.3" | 11.2" | 6.2" | −0.9% | |
| 325/35R22 | 31.0" | 12.8" | 4.5" | +1.1% | |
| 285/40R22 | 31.0" | 11.2" | 4.5" | +1.2% |
Actual speed when the speedometer is calibrated for 245/55R20.
| Speedometer shows | on 265/55R20 | on 245/60R20 | on 255/60R20 |
|---|---|---|---|
| 30 mph | 30.8 mph | 30.9 mph | 31.4 mph |
| 45 mph | 46.3 mph | 46.4 mph | 47.1 mph |
| 60 mph | 61.7 mph | 61.9 mph | 62.8 mph |
| 70 mph | 72.0 mph | 72.2 mph | 73.3 mph |
30.6 inches (778 mm). The sidewall is 5.3 inches.
9.6 inches (245 mm) section width, measured sidewall to sidewall.
About 30.6x9.6R20.
265/55R20 is +2.8% in diameter, within the common 3% guideline. It is 0.8" wider.