35.6" tall, 12.0" wide, 7.8" sidewall
A 305/65R20 tire is 35.6 inches (905 mm) tall and 12.0 inches wide. The sidewall is 65% of the width, 7.8 inches, on a 20-inch wheel, and the tire turns about 566 times per mile.
In flotation terms that is about 35.6x12.0R20. People often call it a 36-inch tire.
The size most often compared with it is 285/70R20, which is 0.1" taller (+0.3%). At an indicated 60 mph you would be doing 60.2 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 305/65R20 | |
|---|---|---|---|---|---|
| 285/70R20 | 35.7" | 11.2" | 7.9" | +0.3% | |
| 325/60R20 | 35.4" | 12.8" | 7.7" | −0.7% | |
| 315/65R20 | 36.1" | 12.4" | 8.1" | +1.4% | |
| 295/65R20 | 35.1" | 11.6" | 7.5" | −1.4% | |
| 35x11.50R20 | 35.0" | 11.5" | 7.5" | −1.7% | |
| 35x12.50R20 | 35.0" | 12.5" | 7.5" | −1.7% | |
| 295/70R20 | 36.3" | 11.6" | 8.1" | +1.8% | |
| 315/60R20 | 34.9" | 12.4" | 7.4" | −2.0% | |
| 285/65R20 | 34.6" | 11.2" | 7.3" | −2.9% | |
| 305/60R20 | 34.4" | 12.0" | 7.2" | −3.4% |
Sizes within 2% of 35.6" on 22" or 18" or 19" wheels.
| Size | Diameter | Width | Sidewall | vs 305/65R20 | |
|---|---|---|---|---|---|
| 245/70R22 | 35.5" | 9.6" | 6.8" | −0.3% | |
| 285/60R22 | 35.5" | 11.2" | 6.7" | −0.4% | |
| 295/75R18 | 35.4" | 11.6" | 8.7" | −0.5% | |
| 305/70R19 | 35.8" | 12.0" | 8.4" | +0.6% | |
| 315/70R18 | 35.4" | 12.4" | 8.7" | −0.7% | |
| 275/80R18 | 35.3" | 10.8" | 8.7" | −0.8% |
Actual speed when the speedometer is calibrated for 305/65R20.
| Speedometer shows | on 285/70R20 | on 325/60R20 | on 315/65R20 |
|---|---|---|---|
| 30 mph | 30.1 mph | 29.8 mph | 30.4 mph |
| 45 mph | 45.1 mph | 44.7 mph | 45.6 mph |
| 60 mph | 60.2 mph | 59.6 mph | 60.9 mph |
| 70 mph | 70.2 mph | 69.5 mph | 71.0 mph |
35.6 inches (905 mm). The sidewall is 7.8 inches.
12.0 inches (305 mm) section width, measured sidewall to sidewall.
About 35.6x12.0R20.
285/70R20 is +0.3% in diameter, within the common 3% guideline. It is 0.8" narrower.