27.8" tall, 12.8" wide, 6.4" sidewall
A 325/50R15 tire is 27.8 inches (706 mm) tall and 12.8 inches wide. The sidewall is 50% of the width, 6.4 inches, on a 15-inch wheel, and the tire turns about 726 times per mile.
In flotation terms that is about 27.8x12.8R15. People often call it a 28-inch tire.
The size most often compared with it is 315/50R15, 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 15" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 325/50R15 | |
|---|---|---|---|---|---|
| 315/50R15 | 27.4" | 12.4" | 6.2" | −1.4% | |
| 305/50R15 | 27.0" | 12.0" | 6.0" | −2.8% | |
| 315/60R15 | 29.9" | 12.4" | 7.4" | +7.5% | |
| 325/60R15 | 30.4" | 12.8" | 7.7" | +9.2% |
Sizes within 2% of 27.8" on 17" wheels.
| Size | Diameter | Width | Sidewall | vs 325/50R15 | |
|---|---|---|---|---|---|
| 275/50R17 | 27.8" | 10.8" | 5.4" | +0.1% | |
| 245/55R17 | 27.6" | 9.6" | 5.3" | −0.7% | |
| 205/65R17 | 27.5" | 8.1" | 5.2" | −1.1% | |
| 265/50R17 | 27.4" | 10.4" | 5.2" | −1.3% |
Actual speed when the speedometer is calibrated for 325/50R15.
| Speedometer shows | on 315/50R15 | on 305/50R15 | on 315/60R15 |
|---|---|---|---|
| 30 mph | 29.6 mph | 29.2 mph | 32.3 mph |
| 45 mph | 44.4 mph | 43.7 mph | 48.4 mph |
| 60 mph | 59.2 mph | 58.3 mph | 64.5 mph |
| 70 mph | 69.0 mph | 68.0 mph | 75.3 mph |
27.8 inches (706 mm). The sidewall is 6.4 inches.
12.8 inches (325 mm) section width, measured sidewall to sidewall.
About 27.8x12.8R15.
315/50R15 is −1.4% in diameter, within the common 3% guideline. It is 0.4" narrower.