36.1" tall, 12.4" wide, 8.1" sidewall
A 315/65R20 tire is 36.1 inches (918 mm) tall and 12.4 inches wide. The sidewall is 65% of the width, 8.1 inches, on a 20-inch wheel, and the tire turns about 558 times per mile.
In flotation terms that is about 36.1x12.4R20. People often call it a 36-inch tire.
The size most often compared with it is 295/70R20, which is 0.1" taller (+0.4%). 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 315/65R20 | |
|---|---|---|---|---|---|
| 295/70R20 | 36.3" | 11.6" | 8.1" | +0.4% | |
| 305/65R20 | 35.6" | 12.0" | 7.8" | −1.4% | |
| 325/60R20 | 35.4" | 12.8" | 7.7" | −2.1% | |
| 37x12.50R20 | 37.0" | 12.5" | 8.5" | +2.4% | |
| 295/65R20 | 35.1" | 11.6" | 7.5" | −2.8% | |
| 35x12.50R20 | 35.0" | 12.5" | 7.5" | −3.1% | |
| 315/60R20 | 34.9" | 12.4" | 7.4" | −3.4% | |
| 305/60R20 | 34.4" | 12.0" | 7.2" | −4.7% | |
| 325/55R20 | 34.1" | 12.8" | 7.0" | −5.7% | |
| 295/60R20 | 33.9" | 11.6" | 7.0" | −6.0% |
Sizes within 2% of 36.1" on 22" or 18" wheels.
| Size | Diameter | Width | Sidewall | vs 315/65R20 | |
|---|---|---|---|---|---|
| 275/65R22 | 36.1" | 10.8" | 7.0" | −0.1% | |
| 325/55R22 | 36.1" | 12.8" | 7.0" | −0.1% | |
| 255/70R22 | 36.1" | 10.0" | 7.0" | −0.2% | |
| 305/75R18 | 36.0" | 12.0" | 9.0" | −0.3% | |
| 285/80R18 | 36.0" | 11.2" | 9.0" | −0.5% | |
| 295/60R22 | 35.9" | 11.6" | 7.0" | −0.5% |
Actual speed when the speedometer is calibrated for 315/65R20.
| Speedometer shows | on 295/70R20 | on 305/65R20 | on 325/60R20 |
|---|---|---|---|
| 30 mph | 30.1 mph | 29.6 mph | 29.4 mph |
| 45 mph | 45.2 mph | 44.4 mph | 44.0 mph |
| 60 mph | 60.2 mph | 59.1 mph | 58.7 mph |
| 70 mph | 70.3 mph | 69.0 mph | 68.5 mph |
36.1 inches (918 mm). The sidewall is 8.1 inches.
12.4 inches (315 mm) section width, measured sidewall to sidewall.
About 36.1x12.4R20.
295/70R20 is +0.4% in diameter, within the common 3% guideline. It is 0.8" narrower.