34.1" tall, 12.8" wide, 7.0" sidewall
A 325/55R20 tire is 34.1 inches (866 mm) tall and 12.8 inches wide. The sidewall is 55% of the width, 7.0 inches, on a 20-inch wheel, and the tire turns about 592 times per mile.
In flotation terms that is about 34.1x12.8R20. People often call it a 34-inch tire.
The size most often compared with it is 305/60R20, which is 0.3" taller (+1.0%). At an indicated 60 mph you would be doing 60.6 mph on it.
| Current | New | Difference |
|---|
| Shows | Actual speed |
|---|
Same 20" wheel, within 20 mm of width and 10 points of aspect ratio.
| Size | Diameter | Width | Sidewall | vs 325/55R20 | |
|---|---|---|---|---|---|
| 305/60R20 | 34.4" | 12.0" | 7.2" | +1.0% | |
| 315/55R20 | 33.6" | 12.4" | 6.8" | −1.3% | |
| 315/60R20 | 34.9" | 12.4" | 7.4" | +2.4% | |
| 305/55R20 | 33.2" | 12.0" | 6.6" | −2.5% | |
| 35x12.50R20 | 35.0" | 12.5" | 7.5" | +2.7% | |
| 35x13.50R20 | 35.0" | 13.5" | 7.5" | +2.7% | |
| 33x12.50R20 | 33.0" | 12.5" | 6.5" | −3.2% | |
| 325/50R20 | 32.8" | 12.8" | 6.4" | −3.8% | |
| 325/60R20 | 35.4" | 12.8" | 7.7" | +3.8% | |
| 305/65R20 | 35.6" | 12.0" | 7.8" | +4.5% |
Sizes within 2% of 34.1" on 18" or 22" wheels.
| Size | Diameter | Width | Sidewall | vs 325/55R20 | |
|---|---|---|---|---|---|
| 255/80R18 | 34.1" | 10.0" | 8.0" | −0.0% | |
| 315/65R18 | 34.1" | 12.4" | 8.1" | +0.1% | |
| 305/50R22 | 34.0" | 12.0" | 6.0" | −0.2% | |
| 275/55R22 | 33.9" | 10.8" | 6.0" | −0.5% | |
| 275/75R18 | 34.2" | 10.8" | 8.1" | +0.5% | |
| 295/70R18 | 34.3" | 11.6" | 8.1" | +0.5% |
Actual speed when the speedometer is calibrated for 325/55R20.
| Speedometer shows | on 305/60R20 | on 315/55R20 | on 315/60R20 |
|---|---|---|---|
| 30 mph | 30.3 mph | 29.6 mph | 30.7 mph |
| 45 mph | 45.4 mph | 44.4 mph | 46.1 mph |
| 60 mph | 60.6 mph | 59.2 mph | 61.4 mph |
| 70 mph | 70.7 mph | 69.1 mph | 71.7 mph |
34.1 inches (866 mm). The sidewall is 7.0 inches.
12.8 inches (325 mm) section width, measured sidewall to sidewall.
About 34.1x12.8R20.
305/60R20 is +1.0% in diameter, within the common 3% guideline. It is 0.8" narrower.