34.1" tall, 10.0" wide, 8.0" sidewall
A 255/80R18 tire is 34.1 inches (865 mm) tall and 10.0 inches wide. The sidewall is 80% of the width, 8.0 inches, on a 18-inch wheel, and the tire turns about 592 times per mile.
In flotation terms that is about 34.1x10.0R18. People often call it a 34-inch tire.
The size most often compared with it is 275/75R18, which is 0.2" taller (+0.5%). At an indicated 60 mph you would be doing 60.3 mph on it.
| Current | New | Difference |
|---|
| Shows | Actual speed |
|---|
Same 18" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 255/80R18 | |
|---|---|---|---|---|---|
| 275/75R18 | 34.2" | 10.8" | 8.1" | +0.5% | |
| 265/75R18 | 33.6" | 10.4" | 7.8" | −1.2% | |
| 265/80R18 | 34.7" | 10.4" | 8.3" | +1.8% | |
| 275/70R18 | 33.2" | 10.8" | 7.6" | −2.7% | |
| 255/75R18 | 33.1" | 10.0" | 7.5" | −2.9% | |
| 275/80R18 | 35.3" | 10.8" | 8.7" | +3.7% | |
| 235/80R18 | 32.8" | 9.3" | 7.4" | −3.7% | |
| 265/70R18 | 32.6" | 10.4" | 7.3" | −4.3% | |
| 245/75R18 | 32.5" | 9.6" | 7.2" | −4.7% | |
| 255/70R18 | 32.1" | 10.0" | 7.0" | −5.9% |
Sizes within 2% of 34.1" on 17" or 20" or 16" wheels.
| Size | Diameter | Width | Sidewall | vs 255/80R18 | |
|---|---|---|---|---|---|
| 255/85R17 | 34.1" | 10.0" | 8.5" | +0.0% | |
| 275/65R20 | 34.1" | 10.8" | 7.0" | +0.0% | |
| 325/55R20 | 34.1" | 12.8" | 7.0" | +0.0% | |
| 305/75R16 | 34.0" | 12.0" | 9.0" | −0.2% | |
| 285/80R16 | 34.0" | 11.2" | 9.0" | −0.3% | |
| 295/60R20 | 33.9" | 11.6" | 7.0" | −0.4% |
Actual speed when the speedometer is calibrated for 255/80R18.
| Speedometer shows | on 275/75R18 | on 265/75R18 | on 265/80R18 |
|---|---|---|---|
| 30 mph | 30.2 mph | 29.6 mph | 30.6 mph |
| 45 mph | 45.2 mph | 44.5 mph | 45.8 mph |
| 60 mph | 60.3 mph | 59.3 mph | 61.1 mph |
| 70 mph | 70.4 mph | 69.2 mph | 71.3 mph |
34.1 inches (865 mm). The sidewall is 8.0 inches.
10.0 inches (255 mm) section width, measured sidewall to sidewall.
About 34.1x10.0R18.
275/75R18 is +0.5% in diameter, within the common 3% guideline. It is 0.8" wider.