36.0" tall, 12.0" wide, 9.0" sidewall
A 305/75R18 tire is 36.0 inches (915 mm) tall and 12.0 inches wide. The sidewall is 75% of the width, 9.0 inches, on a 18-inch wheel, and the tire turns about 560 times per mile.
In flotation terms that is about 36.0x12.0R18. People often call it a 36-inch tire.
The size most often compared with it is 285/80R18, which is 0.1" shorter (−0.2%). At an indicated 60 mph you would be doing 59.9 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 305/75R18 | |
|---|---|---|---|---|---|
| 285/80R18 | 36.0" | 11.2" | 9.0" | −0.2% | |
| 325/70R18 | 35.9" | 12.8" | 9.0" | −0.3% | |
| 295/75R18 | 35.4" | 11.6" | 8.7" | −1.6% | |
| 315/70R18 | 35.4" | 12.4" | 8.7" | −1.8% | |
| 37x12.50R18 | 37.0" | 12.5" | 9.5" | +2.7% | |
| 35x12.50R18 | 35.0" | 12.5" | 8.5" | −2.8% | |
| 285/75R18 | 34.8" | 11.2" | 8.4" | −3.3% | |
| 305/70R18 | 34.8" | 12.0" | 8.4" | −3.3% | |
| 325/65R18 | 34.6" | 12.8" | 8.3" | −3.8% | |
| 295/70R18 | 34.3" | 11.6" | 8.1" | −4.9% |
Sizes within 2% of 36.0" on 17" or 20" or 16" or 19" wheels.
| Size | Diameter | Width | Sidewall | vs 305/75R18 | |
|---|---|---|---|---|---|
| 285/85R17 | 36.1" | 11.2" | 9.5" | +0.2% | |
| 315/65R20 | 36.1" | 12.4" | 8.1" | +0.3% | |
| 315/80R16 | 35.8" | 12.4" | 9.9" | −0.5% | |
| 305/70R19 | 35.8" | 12.0" | 8.4" | −0.6% | |
| 275/75R20 | 36.2" | 10.8" | 8.1" | +0.6% | |
| 295/70R20 | 36.3" | 11.6" | 8.1" | +0.7% |
Actual speed when the speedometer is calibrated for 305/75R18.
| Speedometer shows | on 285/80R18 | on 325/70R18 | on 295/75R18 |
|---|---|---|---|
| 30 mph | 30.0 mph | 29.9 mph | 29.5 mph |
| 45 mph | 44.9 mph | 44.9 mph | 44.3 mph |
| 60 mph | 59.9 mph | 59.8 mph | 59.0 mph |
| 70 mph | 69.9 mph | 69.8 mph | 68.9 mph |
36.0 inches (915 mm). The sidewall is 9.0 inches.
12.0 inches (305 mm) section width, measured sidewall to sidewall.
About 36.0x12.0R18.
285/80R18 is −0.2% in diameter, within the common 3% guideline. It is 0.8" narrower.