36.0" tall, 11.2" wide, 9.0" sidewall
A 285/80R18 tire is 36.0 inches (913 mm) tall and 11.2 inches wide. The sidewall is 80% of the width, 9.0 inches, on a 18-inch wheel, and the tire turns about 561 times per mile.
In flotation terms that is about 36.0x11.2R18. People often call it a 36-inch tire.
The size most often compared with it is 305/75R18, which is 0.1" taller (+0.2%). At an indicated 60 mph you would be doing 60.1 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 285/80R18 | |
|---|---|---|---|---|---|
| 305/75R18 | 36.0" | 12.0" | 9.0" | +0.2% | |
| 275/85R18 | 36.4" | 10.8" | 9.2" | +1.3% | |
| 295/75R18 | 35.4" | 11.6" | 8.7" | −1.5% | |
| 275/80R18 | 35.3" | 10.8" | 8.7" | −1.8% | |
| 285/75R18 | 34.8" | 11.2" | 8.4" | −3.1% | |
| 305/70R18 | 34.8" | 12.0" | 8.4" | −3.2% | |
| 265/80R18 | 34.7" | 10.4" | 8.3" | −3.5% | |
| 295/70R18 | 34.3" | 11.6" | 8.1" | −4.7% | |
| 275/75R18 | 34.2" | 10.8" | 8.1" | −4.8% | |
| 285/70R18 | 33.7" | 11.2" | 7.9" | −6.2% |
Sizes within 2% of 36.0" on 16" or 17" or 19" or 20" wheels.
| Size | Diameter | Width | Sidewall | vs 285/80R18 | |
|---|---|---|---|---|---|
| 315/80R16 | 35.8" | 12.4" | 9.9" | −0.3% | |
| 285/85R17 | 36.1" | 11.2" | 9.5" | +0.3% | |
| 305/70R19 | 35.8" | 12.0" | 8.4" | −0.4% | |
| 315/65R20 | 36.1" | 12.4" | 8.1" | +0.5% | |
| 285/70R20 | 35.7" | 11.2" | 7.9" | −0.7% | |
| 275/75R20 | 36.2" | 10.8" | 8.1" | +0.8% |
Actual speed when the speedometer is calibrated for 285/80R18.
| Speedometer shows | on 305/75R18 | on 275/85R18 | on 295/75R18 |
|---|---|---|---|
| 30 mph | 30.0 mph | 30.4 mph | 29.6 mph |
| 45 mph | 45.1 mph | 45.6 mph | 44.3 mph |
| 60 mph | 60.1 mph | 60.8 mph | 59.1 mph |
| 70 mph | 70.1 mph | 70.9 mph | 69.0 mph |
36.0 inches (913 mm). The sidewall is 9.0 inches.
11.2 inches (285 mm) section width, measured sidewall to sidewall.
About 36.0x11.2R18.
305/75R18 is +0.2% in diameter, within the common 3% guideline. It is 0.8" wider.