32.1" tall, 10.0" wide, 8.5" sidewall
A 255/85R15 tire is 32.1 inches (815 mm) tall and 10.0 inches wide. The sidewall is 85% of the width, 8.5 inches, on a 15-inch wheel, and the tire turns about 629 times per mile.
In flotation terms that is about 32.1x10.0R15, closest to the common 32x11.50R15 (32.0"). People often call it a 32-inch tire.
The size most often compared with it is 265/85R15, which is 0.7" taller (+2.1%). At an indicated 60 mph you would be doing 61.3 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 255/85R15 | |
|---|---|---|---|---|---|
| 265/85R15 | 32.7" | 10.4" | 8.9" | +2.1% | |
| 275/75R15 | 31.2" | 10.8" | 8.1" | −2.6% | |
| 33x10.50R15 | 33.0" | 10.5" | 9.0" | +2.9% | |
| 31x10.50R15 | 31.0" | 10.5" | 8.0" | −3.3% | |
| 235/85R15 | 30.7" | 9.3" | 7.9" | −4.2% | |
| 265/75R15 | 30.6" | 10.4" | 7.8" | −4.4% | |
| 255/75R15 | 30.1" | 10.0" | 7.5" | −6.3% | |
| 30x9.50R15 | 30.0" | 9.5" | 7.5" | −6.4% | |
| 245/75R15 | 29.5" | 9.6" | 7.2" | −8.1% | |
| 235/75R15 | 28.9" | 9.3" | 6.9" | −9.9% |
Sizes within 2% of 32.1" on 16" or 17" wheels.
| Size | Diameter | Width | Sidewall | vs 255/85R15 | |
|---|---|---|---|---|---|
| 255/80R16 | 32.1" | 10.0" | 8.0" | −0.0% | |
| 255/75R17 | 32.1" | 10.0" | 7.5" | −0.0% | |
| 295/65R17 | 32.1" | 11.6" | 7.5" | +0.1% | |
| 275/70R17 | 32.2" | 10.8" | 7.6" | +0.3% | |
| 275/75R16 | 32.2" | 10.8" | 8.1" | +0.5% | |
| 315/60R17 | 31.9" | 12.4" | 7.4" | −0.6% |
Actual speed when the speedometer is calibrated for 255/85R15.
| Speedometer shows | on 265/85R15 | on 275/75R15 | on 33x10.50R15 |
|---|---|---|---|
| 30 mph | 30.6 mph | 29.2 mph | 30.9 mph |
| 45 mph | 45.9 mph | 43.8 mph | 46.3 mph |
| 60 mph | 61.3 mph | 58.5 mph | 61.7 mph |
| 70 mph | 71.5 mph | 68.2 mph | 72.0 mph |
32.1 inches (815 mm). The sidewall is 8.5 inches.
10.0 inches (255 mm) section width, measured sidewall to sidewall.
About 32.1x10.0R15; the closest common flotation size is 32x11.50R15 at 32.0".
265/85R15 is +2.1% in diameter, within the common 3% guideline. It is 0.4" wider.