28.1" tall, 11.2" wide, 5.0" sidewall
A 285/45R18 tire is 28.1 inches (714 mm) tall and 11.2 inches wide. The sidewall is 45% of the width, 5.0 inches, on a 18-inch wheel, and the tire turns about 718 times per mile.
In flotation terms that is about 28.1x11.2R18. People often call it a 28-inch tire.
The size most often compared with it is 265/50R18, which is 0.3" taller (+1.2%). At an indicated 60 mph you would be doing 60.7 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 285/45R18 | |
|---|---|---|---|---|---|
| 265/50R18 | 28.4" | 10.4" | 5.2" | +1.2% | |
| 295/45R18 | 28.5" | 11.6" | 5.2" | +1.3% | |
| 275/45R18 | 27.7" | 10.8" | 4.9" | −1.3% | |
| 275/50R18 | 28.8" | 10.8" | 5.4" | +2.6% | |
| 295/40R18 | 27.3" | 11.6" | 4.6" | −2.9% | |
| 285/50R18 | 29.2" | 11.2" | 5.6" | +4.0% | |
| 285/40R18 | 27.0" | 11.2" | 4.5" | −4.0% | |
| 265/55R18 | 29.5" | 10.4" | 5.7" | +4.9% | |
| 275/40R18 | 26.7" | 10.8" | 4.3" | −5.1% | |
| 305/35R18 | 26.4" | 12.0" | 4.2" | −6.0% |
Sizes within 2% of 28.1" on 20" or 17" or 16" wheels.
| Size | Diameter | Width | Sidewall | vs 285/45R18 | |
|---|---|---|---|---|---|
| 295/35R20 | 28.1" | 11.6" | 4.1" | +0.1% | |
| 345/30R20 | 28.1" | 13.6" | 4.1" | +0.2% | |
| 285/35R20 | 27.9" | 11.2" | 3.9" | −0.9% | |
| 275/50R17 | 27.8" | 10.8" | 5.4" | −1.0% | |
| 325/45R17 | 28.5" | 12.8" | 5.8" | +1.5% | |
| 245/65R16 | 28.5" | 9.6" | 6.3" | +1.6% |
Actual speed when the speedometer is calibrated for 285/45R18.
| Speedometer shows | on 265/50R18 | on 295/45R18 | on 275/45R18 |
|---|---|---|---|
| 30 mph | 30.4 mph | 30.4 mph | 29.6 mph |
| 45 mph | 45.5 mph | 45.6 mph | 44.4 mph |
| 60 mph | 60.7 mph | 60.8 mph | 59.2 mph |
| 70 mph | 70.8 mph | 70.9 mph | 69.1 mph |
28.1 inches (714 mm). The sidewall is 5.0 inches.
11.2 inches (285 mm) section width, measured sidewall to sidewall.
About 28.1x11.2R18.
265/50R18 is +1.2% in diameter, within the common 3% guideline. It is 0.8" narrower.