35.4" tall, 12.4" wide, 8.7" sidewall
A 315/70R18 tire is 35.4 inches (898 mm) tall and 12.4 inches wide. The sidewall is 70% of the width, 8.7 inches, on a 18-inch wheel, and the tire turns about 570 times per mile.
In flotation terms that is about 35.4x12.4R18, closest to the common 35x12.50R18 (35.0"). People often call it a 35-inch tire.
The size most often compared with it is 295/75R18, 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 315/70R18 | |
|---|---|---|---|---|---|
| 295/75R18 | 35.4" | 11.6" | 8.7" | +0.2% | |
| 35x12.50R18 | 35.0" | 12.5" | 8.5" | −1.0% | |
| 305/70R18 | 34.8" | 12.0" | 8.4" | −1.6% | |
| 325/70R18 | 35.9" | 12.8" | 9.0" | +1.6% | |
| 305/75R18 | 36.0" | 12.0" | 9.0" | +1.8% | |
| 325/65R18 | 34.6" | 12.8" | 8.3" | −2.1% | |
| 295/70R18 | 34.3" | 11.6" | 8.1" | −3.1% | |
| 315/65R18 | 34.1" | 12.4" | 8.1" | −3.5% | |
| 37x12.50R18 | 37.0" | 12.5" | 9.5" | +4.6% | |
| 305/65R18 | 33.6" | 12.0" | 7.8" | −5.0% |
Sizes within 2% of 35.4" on 20" or 17" or 16" wheels.
| Size | Diameter | Width | Sidewall | vs 315/70R18 | |
|---|---|---|---|---|---|
| 325/60R20 | 35.4" | 12.8" | 7.7" | −0.0% | |
| 275/85R17 | 35.4" | 10.8" | 9.2" | +0.1% | |
| 325/75R16 | 35.2" | 12.8" | 9.6" | −0.5% | |
| 275/70R20 | 35.2" | 10.8" | 7.6" | −0.6% | |
| 295/80R17 | 35.6" | 11.6" | 9.3" | +0.6% | |
| 315/75R17 | 35.6" | 12.4" | 9.3" | +0.7% |
Actual speed when the speedometer is calibrated for 315/70R18.
| Speedometer shows | on 295/75R18 | on 35x12.50R18 | on 305/70R18 |
|---|---|---|---|
| 30 mph | 30.1 mph | 29.7 mph | 29.5 mph |
| 45 mph | 45.1 mph | 44.5 mph | 44.3 mph |
| 60 mph | 60.1 mph | 59.4 mph | 59.1 mph |
| 70 mph | 70.1 mph | 69.3 mph | 68.9 mph |
35.4 inches (898 mm). The sidewall is 8.7 inches.
12.4 inches (315 mm) section width, measured sidewall to sidewall.
About 35.4x12.4R18; the closest common flotation size is 35x12.50R18 at 35.0".
295/75R18 is +0.2% in diameter, within the common 3% guideline. It is 0.8" narrower.