34.1" tall, 12.4" wide, 8.1" sidewall
A 315/65R18 tire is 34.1 inches (867 mm) tall and 12.4 inches wide. The sidewall is 65% of the width, 8.1 inches, on a 18-inch wheel, and the tire turns about 591 times per mile.
In flotation terms that is about 34.1x12.4R18. People often call it a 34-inch tire.
The size most often compared with it is 295/70R18, which is 0.1" taller (+0.4%). At an indicated 60 mph you would be doing 60.2 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 315/65R18 | |
|---|---|---|---|---|---|
| 295/70R18 | 34.3" | 11.6" | 8.1" | +0.4% | |
| 325/65R18 | 34.6" | 12.8" | 8.3" | +1.5% | |
| 305/65R18 | 33.6" | 12.0" | 7.8" | −1.5% | |
| 305/70R18 | 34.8" | 12.0" | 8.4" | +2.0% | |
| 325/60R18 | 33.4" | 12.8" | 7.7" | −2.2% | |
| 35x12.50R18 | 35.0" | 12.5" | 8.5" | +2.6% | |
| 295/65R18 | 33.1" | 11.6" | 7.5" | −3.0% | |
| 33x12.50R18 | 33.0" | 12.5" | 7.5" | −3.3% | |
| 315/70R18 | 35.4" | 12.4" | 8.7" | +3.6% | |
| 295/75R18 | 35.4" | 11.6" | 8.7" | +3.8% |
Sizes within 2% of 34.1" on 20" or 17" or 16" wheels.
| Size | Diameter | Width | Sidewall | vs 315/65R18 | |
|---|---|---|---|---|---|
| 275/65R20 | 34.1" | 10.8" | 7.0" | −0.1% | |
| 325/55R20 | 34.1" | 12.8" | 7.0" | −0.1% | |
| 255/85R17 | 34.1" | 10.0" | 8.5" | −0.2% | |
| 305/75R16 | 34.0" | 12.0" | 9.0" | −0.3% | |
| 285/80R16 | 34.0" | 11.2" | 9.0" | −0.5% | |
| 295/60R20 | 33.9" | 11.6" | 7.0" | −0.5% |
Actual speed when the speedometer is calibrated for 315/65R18.
| Speedometer shows | on 295/70R18 | on 325/65R18 | on 305/65R18 |
|---|---|---|---|
| 30 mph | 30.1 mph | 30.4 mph | 29.6 mph |
| 45 mph | 45.2 mph | 45.7 mph | 44.3 mph |
| 60 mph | 60.2 mph | 60.9 mph | 59.1 mph |
| 70 mph | 70.3 mph | 71.0 mph | 69.0 mph |
34.1 inches (867 mm). The sidewall is 8.1 inches.
12.4 inches (315 mm) section width, measured sidewall to sidewall.
About 34.1x12.4R18.
295/70R18 is +0.4% in diameter, within the common 3% guideline. It is 0.8" narrower.