30.4" tall, 12.8" wide, 7.7" sidewall
A 325/60R15 tire is 30.4 inches (771 mm) tall and 12.8 inches wide. The sidewall is 60% of the width, 7.7 inches, on a 15-inch wheel, and the tire turns about 664 times per mile.
In flotation terms that is about 30.4x12.8R15, closest to the common 30x9.50R15 (30.0"). People often call it a 30-inch tire.
The size most often compared with it is 315/60R15, which is 0.5" shorter (−1.6%). At an indicated 60 mph you would be doing 59.1 mph on it.
| Current | New | Difference |
|---|
| Shows | Actual speed |
|---|
Same 15" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 325/60R15 | |
|---|---|---|---|---|---|
| 315/60R15 | 29.9" | 12.4" | 7.4" | −1.6% | |
| 305/70R15 | 31.8" | 12.0" | 8.4" | +4.8% | |
| 315/70R15 | 32.4" | 12.4" | 8.7" | +6.6% | |
| 325/50R15 | 27.8" | 12.8" | 6.4" | −8.4% | |
| 315/50R15 | 27.4" | 12.4" | 6.2" | −9.7% | |
| 305/50R15 | 27.0" | 12.0" | 6.0" | −11.0% |
Sizes within 2% of 30.4" on 16" or 17" wheels.
| Size | Diameter | Width | Sidewall | vs 325/60R15 | |
|---|---|---|---|---|---|
| 215/85R16 | 30.4" | 8.5" | 7.2" | +0.1% | |
| 225/75R17 | 30.3" | 8.9" | 6.6" | −0.2% | |
| 285/60R17 | 30.5" | 11.2" | 6.7" | +0.4% | |
| 245/75R16 | 30.5" | 9.6" | 7.2" | +0.4% | |
| 305/55R17 | 30.2" | 12.0" | 6.6" | −0.5% | |
| 245/70R17 | 30.5" | 9.6" | 6.8" | +0.5% |
Actual speed when the speedometer is calibrated for 325/60R15.
| Speedometer shows | on 315/60R15 | on 305/70R15 | on 315/70R15 |
|---|---|---|---|
| 30 mph | 29.5 mph | 31.4 mph | 32.0 mph |
| 45 mph | 44.3 mph | 47.2 mph | 48.0 mph |
| 60 mph | 59.1 mph | 62.9 mph | 64.0 mph |
| 70 mph | 68.9 mph | 73.4 mph | 74.6 mph |
30.4 inches (771 mm). The sidewall is 7.7 inches.
12.8 inches (325 mm) section width, measured sidewall to sidewall.
About 30.4x12.8R15; the closest common flotation size is 30x9.50R15 at 30.0".
315/60R15 is −1.6% in diameter, within the common 3% guideline. It is 0.4" narrower.