33.7" tall, 11.2" wide, 7.9" sidewall
A 285/70R18 tire is 33.7 inches (856 mm) tall and 11.2 inches wide. The sidewall is 70% of the width, 7.9 inches, on a 18-inch wheel, and the tire turns about 598 times per mile.
In flotation terms that is about 33.7x11.2R18. People often call it a 34-inch tire.
The size most often compared with it is 275/70R18, which is 0.6" shorter (−1.6%). At an indicated 60 mph you would be doing 59.0 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 285/70R18 | |
|---|---|---|---|---|---|
| 265/75R18 | 33.6" | 10.4" | 7.8" | −0.2% | |
| 305/65R18 | 33.6" | 12.0" | 7.8" | −0.3% | |
| 275/75R18 | 34.2" | 10.8" | 8.1" | +1.6% | |
| 295/70R18 | 34.3" | 11.6" | 8.1" | +1.6% | compare |
| 275/70R18 | 33.2" | 10.8" | 7.6" | −1.6% | compare |
| 295/65R18 | 33.1" | 11.6" | 7.5" | −1.8% | |
| 265/80R18 | 34.7" | 10.4" | 8.3" | +2.9% | |
| 265/70R18 | 32.6" | 10.4" | 7.3" | −3.3% | |
| 305/70R18 | 34.8" | 12.0" | 8.4" | +3.3% | |
| 285/65R18 | 32.6" | 11.2" | 7.3" | −3.3% | compare |
Sizes within 2% of 33.7" on 17" or 16" or 20" or 19" wheels.
| Size | Diameter | Width | Sidewall | vs 285/70R18 | |
|---|---|---|---|---|---|
| 265/80R17 | 33.7" | 10.4" | 8.3" | −0.0% | |
| 265/85R16 | 33.7" | 10.4" | 8.9" | +0.1% | |
| 315/55R20 | 33.6" | 12.4" | 6.8" | −0.2% | |
| 305/70R17 | 33.8" | 12.0" | 8.4" | +0.3% | |
| 265/70R19 | 33.6" | 10.4" | 7.3" | −0.3% | |
| 285/75R17 | 33.8" | 11.2" | 8.4" | +0.4% |
Actual speed when the speedometer is calibrated for 285/70R18.
| Speedometer shows | on 275/70R18 | on 285/65R18 | on 295/70R18 |
|---|---|---|---|
| 30 mph | 29.5 mph | 29.0 mph | 30.5 mph |
| 45 mph | 44.3 mph | 43.5 mph | 45.7 mph |
| 60 mph | 59.0 mph | 58.0 mph | 61.0 mph |
| 70 mph | 68.9 mph | 67.7 mph | 71.1 mph |
33.7 inches (856 mm). The sidewall is 7.9 inches.
11.2 inches (285 mm) section width, measured sidewall to sidewall.
About 33.7x11.2R18.
275/70R18 is −1.6% in diameter, within the common 3% guideline. It is 0.4" narrower.