32.1" tall, 10.0" wide, 7.0" sidewall
A 255/70R18 tire is 32.1 inches (814 mm) tall and 10.0 inches wide. The sidewall is 70% of the width, 7.0 inches, on a 18-inch wheel, and the tire turns about 629 times per mile.
In flotation terms that is about 32.1x10.0R18. People often call it a 32-inch tire.
The size most often compared with it is 275/65R18, which is 0.0" taller (+0.1%). At an indicated 60 mph you would be doing 60.0 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 255/70R18 | |
|---|---|---|---|---|---|
| 275/65R18 | 32.1" | 10.8" | 7.0" | +0.1% | compare |
| 235/75R18 | 31.9" | 9.3" | 6.9" | −0.6% | |
| 245/75R18 | 32.5" | 9.6" | 7.2" | +1.3% | |
| 265/65R18 | 31.6" | 10.4" | 6.8" | −1.5% | |
| 265/70R18 | 32.6" | 10.4" | 7.3" | +1.7% | |
| 245/70R18 | 31.5" | 9.6" | 6.8" | −1.7% | |
| 235/80R18 | 32.8" | 9.3" | 7.4" | +2.3% | |
| 255/75R18 | 33.1" | 10.0" | 7.5" | +3.1% | |
| 275/60R18 | 31.0" | 10.8" | 6.5" | −3.3% | |
| 275/70R18 | 33.2" | 10.8" | 7.6" | +3.4% |
Sizes within 2% of 32.1" on 17" or 16" or 20" wheels.
| Size | Diameter | Width | Sidewall | vs 255/70R18 | |
|---|---|---|---|---|---|
| 255/75R17 | 32.1" | 10.0" | 7.5" | +0.0% | |
| 255/80R16 | 32.1" | 10.0" | 8.0" | +0.0% | |
| 255/60R20 | 32.0" | 10.0" | 6.0" | −0.0% | |
| 295/65R17 | 32.1" | 11.6" | 7.5" | +0.1% | |
| 305/50R20 | 32.0" | 12.0" | 6.0" | −0.1% | |
| 275/70R17 | 32.2" | 10.8" | 7.6" | +0.3% |
Actual speed when the speedometer is calibrated for 255/70R18.
| Speedometer shows | on 275/65R18 | on 235/75R18 | on 245/75R18 |
|---|---|---|---|
| 30 mph | 30.0 mph | 29.8 mph | 30.4 mph |
| 45 mph | 45.0 mph | 44.8 mph | 45.6 mph |
| 60 mph | 60.0 mph | 59.7 mph | 60.8 mph |
| 70 mph | 70.0 mph | 69.6 mph | 70.9 mph |
32.1 inches (814 mm). The sidewall is 7.0 inches.
10.0 inches (255 mm) section width, measured sidewall to sidewall.
About 32.1x10.0R18.
275/65R18 is +0.1% in diameter, within the common 3% guideline. It is 0.8" wider.