33.6" tall, 12.4" wide, 6.8" sidewall
A 315/55R20 tire is 33.6 inches (855 mm) tall and 12.4 inches wide. The sidewall is 55% of the width, 6.8 inches, on a 20-inch wheel, and the tire turns about 599 times per mile.
In flotation terms that is about 33.6x12.4R20. People often call it a 34-inch tire.
The size most often compared with it is 295/60R20, which is 0.3" taller (+0.9%). At an indicated 60 mph you would be doing 60.5 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 315/55R20 | |
|---|---|---|---|---|---|
| 295/60R20 | 33.9" | 11.6" | 7.0" | +0.9% | |
| 305/55R20 | 33.2" | 12.0" | 6.6" | −1.3% | |
| 325/55R20 | 34.1" | 12.8" | 7.0" | +1.3% | |
| 33x12.50R20 | 33.0" | 12.5" | 6.5" | −1.9% | |
| 305/60R20 | 34.4" | 12.0" | 7.2" | +2.3% | |
| 325/50R20 | 32.8" | 12.8" | 6.4" | −2.5% | |
| 295/55R20 | 32.8" | 11.6" | 6.4" | −2.6% | |
| 315/60R20 | 34.9" | 12.4" | 7.4" | +3.7% | |
| 315/50R20 | 32.4" | 12.4" | 6.2" | −3.7% | |
| 35x12.50R20 | 35.0" | 12.5" | 7.5" | +4.0% |
Sizes within 2% of 33.6" on 18" or 22" or 19" wheels.
| Size | Diameter | Width | Sidewall | vs 315/55R20 | |
|---|---|---|---|---|---|
| 265/75R18 | 33.6" | 10.4" | 7.8" | +0.0% | |
| 295/50R22 | 33.6" | 11.6" | 5.8" | −0.1% | |
| 305/65R18 | 33.6" | 12.0" | 7.8" | −0.1% | |
| 265/70R19 | 33.6" | 10.4" | 7.3" | −0.1% | |
| 285/70R18 | 33.7" | 11.2" | 7.9" | +0.2% | |
| 325/45R22 | 33.5" | 12.8" | 5.8" | −0.4% |
Actual speed when the speedometer is calibrated for 315/55R20.
| Speedometer shows | on 295/60R20 | on 305/55R20 | on 325/55R20 |
|---|---|---|---|
| 30 mph | 30.3 mph | 29.6 mph | 30.4 mph |
| 45 mph | 45.4 mph | 44.4 mph | 45.6 mph |
| 60 mph | 60.5 mph | 59.2 mph | 60.8 mph |
| 70 mph | 70.6 mph | 69.1 mph | 70.9 mph |
33.6 inches (855 mm). The sidewall is 6.8 inches.
12.4 inches (315 mm) section width, measured sidewall to sidewall.
About 33.6x12.4R20.
295/60R20 is +0.9% in diameter, within the common 3% guideline. It is 0.8" narrower.