34.8" tall, 12.0" wide, 8.4" sidewall
A 305/70R18 tire is 34.8 inches (884 mm) tall and 12.0 inches wide. The sidewall is 70% of the width, 8.4 inches, on a 18-inch wheel, and the tire turns about 579 times per mile.
In flotation terms that is about 34.8x12.0R18, closest to the common 35x12.50R18 (35.0"). People often call it a 35-inch tire.
The size most often compared with it is 285/75R18, 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 |
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Same 18" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 305/70R18 | |
|---|---|---|---|---|---|
| 285/75R18 | 34.8" | 11.2" | 8.4" | +0.1% | compare |
| 325/65R18 | 34.6" | 12.8" | 8.3" | −0.5% | |
| 35x12.50R18 | 35.0" | 12.5" | 8.5" | +0.5% | compare |
| 295/70R18 | 34.3" | 11.6" | 8.1" | −1.6% | compare |
| 315/70R18 | 35.4" | 12.4" | 8.7" | +1.6% | |
| 295/75R18 | 35.4" | 11.6" | 8.7" | +1.8% | |
| 315/65R18 | 34.1" | 12.4" | 8.1" | −2.0% | |
| 325/70R18 | 35.9" | 12.8" | 9.0" | +3.2% | |
| 285/70R18 | 33.7" | 11.2" | 7.9" | −3.2% | |
| 285/80R18 | 36.0" | 11.2" | 9.0" | +3.3% |
Sizes within 2% of 34.8" on 20" or 17" wheels.
| Size | Diameter | Width | Sidewall | vs 305/70R18 | |
|---|---|---|---|---|---|
| 315/60R20 | 34.9" | 12.4" | 7.4" | +0.2% | |
| 265/85R17 | 34.7" | 10.4" | 8.9" | −0.2% | |
| 325/70R17 | 34.9" | 12.8" | 9.0" | +0.3% | |
| 285/80R17 | 35.0" | 11.2" | 9.0" | +0.4% | |
| 35x11.50R17 | 35.0" | 11.5" | 9.0" | +0.5% | |
| 35x11.50R20 | 35.0" | 11.5" | 7.5" | +0.5% |
Actual speed when the speedometer is calibrated for 305/70R18.
| Speedometer shows | on 285/75R18 | on 295/70R18 | on 35x12.50R18 |
|---|---|---|---|
| 30 mph | 30.0 mph | 29.5 mph | 30.2 mph |
| 45 mph | 45.0 mph | 44.3 mph | 45.2 mph |
| 60 mph | 60.0 mph | 59.0 mph | 60.3 mph |
| 70 mph | 70.0 mph | 68.9 mph | 70.4 mph |
34.8 inches (884 mm). The sidewall is 8.4 inches.
12.0 inches (305 mm) section width, measured sidewall to sidewall.
About 34.8x12.0R18; the closest common flotation size is 35x12.50R18 at 35.0".
285/75R18 is +0.1% in diameter, within the common 3% guideline. It is 0.8" narrower.