34.6" tall, 12.8" wide, 8.3" sidewall
A 325/65R18 tire is 34.6 inches (880 mm) tall and 12.8 inches wide. The sidewall is 65% of the width, 8.3 inches, on a 18-inch wheel, and the tire turns about 582 times per mile.
In flotation terms that is about 34.6x12.8R18, closest to the common 35x12.50R18 (35.0"). People often call it a 35-inch tire.
The size most often compared with it is 275/70R18, which is 1.5" shorter (−4.3%). At an indicated 60 mph you would be doing 57.4 mph on it, more than the 3% change many shops use as a limit.
| 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 325/65R18 | |
|---|---|---|---|---|---|
| 305/70R18 | 34.8" | 12.0" | 8.4" | +0.5% | |
| 35x12.50R18 | 35.0" | 12.5" | 8.5" | +1.1% | |
| 315/65R18 | 34.1" | 12.4" | 8.1" | −1.5% | |
| 315/70R18 | 35.4" | 12.4" | 8.7" | +2.1% | |
| 305/65R18 | 33.6" | 12.0" | 7.8" | −3.0% | |
| 325/60R18 | 33.4" | 12.8" | 7.7" | −3.7% | |
| 325/70R18 | 35.9" | 12.8" | 9.0" | +3.7% | |
| 305/75R18 | 36.0" | 12.0" | 9.0" | +4.0% | |
| 33x12.50R18 | 33.0" | 12.5" | 7.5" | −4.7% | |
| 305/60R18 | 32.4" | 12.0" | 7.2" | −6.4% |
Sizes within 2% of 34.6" on 20" or 16" or 17" wheels.
| Size | Diameter | Width | Sidewall | vs 325/65R18 | |
|---|---|---|---|---|---|
| 265/70R20 | 34.6" | 10.4" | 7.3" | −0.1% | |
| 315/75R16 | 34.6" | 12.4" | 9.3" | −0.1% | |
| 285/65R20 | 34.6" | 11.2" | 7.3" | −0.1% | |
| 265/85R17 | 34.7" | 10.4" | 8.9" | +0.3% | |
| 295/75R17 | 34.4" | 11.6" | 8.7" | −0.6% | |
| 305/60R20 | 34.4" | 12.0" | 7.2" | −0.6% |
Actual speed when the speedometer is calibrated for 325/65R18.
| Speedometer shows | on 275/70R18 | on 295/70R18 | on 305/70R18 |
|---|---|---|---|
| 30 mph | 28.7 mph | 29.7 mph | 30.2 mph |
| 45 mph | 43.1 mph | 44.5 mph | 45.2 mph |
| 60 mph | 57.4 mph | 59.4 mph | 60.3 mph |
| 70 mph | 67.0 mph | 69.2 mph | 70.4 mph |
34.6 inches (880 mm). The sidewall is 8.3 inches.
12.8 inches (325 mm) section width, measured sidewall to sidewall.
About 34.6x12.8R18; the closest common flotation size is 35x12.50R18 at 35.0".
275/70R18 is −4.3% in diameter, more than the common 3% guideline, so expect a speedometer error and check clearance. It is 2.0" narrower.