30.6" tall, 12.4" wide, 6.8" sidewall
A 315/55R17 tire is 30.6 inches (778 mm) tall and 12.4 inches wide. The sidewall is 55% of the width, 6.8 inches, on a 17-inch wheel, and the tire turns about 658 times per mile.
In flotation terms that is about 30.6x12.4R17. People often call it a 31-inch tire.
The size most often compared with it is 305/55R17, which is 0.4" shorter (−1.4%). At an indicated 60 mph you would be doing 59.2 mph on it.
| Current | New | Difference |
|---|
| Shows | Actual speed |
|---|
Same 17" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 315/55R17 | |
|---|---|---|---|---|---|
| 305/55R17 | 30.2" | 12.0" | 6.6" | −1.4% | |
| 305/60R17 | 31.4" | 12.0" | 7.2" | +2.5% | |
| 315/50R17 | 29.4" | 12.4" | 6.2" | −4.0% | |
| 315/60R17 | 31.9" | 12.4" | 7.4" | +4.0% | |
| 295/65R17 | 32.1" | 11.6" | 7.5" | +4.8% | |
| 305/65R17 | 32.6" | 12.0" | 7.8" | +6.4% | |
| 325/45R17 | 28.5" | 12.8" | 5.8" | −6.9% | |
| 33x12.50R17 | 33.0" | 12.5" | 8.0" | +7.7% | |
| 315/65R17 | 33.1" | 12.4" | 8.1" | +8.1% |
Sizes within 2% of 30.6" on 15" or 16" or 18" wheels.
| Size | Diameter | Width | Sidewall | vs 315/55R17 | |
|---|---|---|---|---|---|
| 265/75R15 | 30.6" | 10.4" | 7.8" | +0.0% | |
| 265/70R16 | 30.6" | 10.4" | 7.3" | −0.1% | |
| 285/65R16 | 30.6" | 11.2" | 7.3" | −0.2% | |
| 285/70R15 | 30.7" | 11.2" | 7.9" | +0.2% | |
| 235/85R15 | 30.7" | 9.3" | 7.9" | +0.3% | |
| 245/65R18 | 30.5" | 9.6" | 6.3" | −0.3% |
Actual speed when the speedometer is calibrated for 315/55R17.
| Speedometer shows | on 305/55R17 | on 305/60R17 | on 315/50R17 |
|---|---|---|---|
| 30 mph | 29.6 mph | 30.8 mph | 28.8 mph |
| 45 mph | 44.4 mph | 46.1 mph | 43.2 mph |
| 60 mph | 59.2 mph | 61.5 mph | 57.6 mph |
| 70 mph | 69.0 mph | 71.8 mph | 67.2 mph |
30.6 inches (778 mm). The sidewall is 6.8 inches.
12.4 inches (315 mm) section width, measured sidewall to sidewall.
About 30.6x12.4R17.
305/55R17 is −1.4% in diameter, within the common 3% guideline. It is 0.4" narrower.