32.8" tall, 12.8" wide, 6.4" sidewall
A 325/50R20 tire is 32.8 inches (833 mm) tall and 12.8 inches wide. The sidewall is 50% of the width, 6.4 inches, on a 20-inch wheel, and the tire turns about 615 times per mile.
In flotation terms that is about 32.8x12.8R20, closest to the common 33x12.50R20 (33.0"). People often call it a 33-inch tire.
The size most often compared with it is 33x12.50R20, which is 0.2" taller (+0.6%). At an indicated 60 mph you would be doing 60.4 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 325/50R20 | |
|---|---|---|---|---|---|
| 33x12.50R20 | 33.0" | 12.5" | 6.5" | +0.6% | |
| 315/50R20 | 32.4" | 12.4" | 6.2" | −1.2% | |
| 305/55R20 | 33.2" | 12.0" | 6.6" | +1.3% | |
| 305/50R20 | 32.0" | 12.0" | 6.0" | −2.4% | |
| 315/55R20 | 33.6" | 12.4" | 6.8" | +2.6% | |
| 325/55R20 | 34.1" | 12.8" | 7.0" | +3.9% | |
| 305/60R20 | 34.4" | 12.0" | 7.2" | +4.9% | |
| 315/45R20 | 31.2" | 12.4" | 5.6" | −5.0% | |
| 305/45R20 | 30.8" | 12.0" | 5.4" | −6.1% | |
| 315/60R20 | 34.9" | 12.4" | 7.4" | +6.4% |
Sizes within 2% of 32.8" on 18" or 22" wheels.
| Size | Diameter | Width | Sidewall | vs 325/50R20 | |
|---|---|---|---|---|---|
| 235/80R18 | 32.8" | 9.3" | 7.4" | +0.0% | |
| 305/45R22 | 32.8" | 12.0" | 5.4" | +0.0% | |
| 265/70R18 | 32.6" | 10.4" | 7.3" | −0.6% | |
| 33x12.50R18 | 33.0" | 12.5" | 7.5" | +0.6% | |
| 33x12.50R22 | 33.0" | 12.5" | 5.5" | +0.6% | |
| 285/65R18 | 32.6" | 11.2" | 7.3" | −0.6% |
Actual speed when the speedometer is calibrated for 325/50R20.
| Speedometer shows | on 33x12.50R20 | on 315/50R20 | on 305/55R20 |
|---|---|---|---|
| 30 mph | 30.2 mph | 29.6 mph | 30.4 mph |
| 45 mph | 45.3 mph | 44.5 mph | 45.6 mph |
| 60 mph | 60.4 mph | 59.3 mph | 60.8 mph |
| 70 mph | 70.4 mph | 69.2 mph | 70.9 mph |
32.8 inches (833 mm). The sidewall is 6.4 inches.
12.8 inches (325 mm) section width, measured sidewall to sidewall.
About 32.8x12.8R20; the closest common flotation size is 33x12.50R20 at 33.0".
33x12.50R20 is +0.6% in diameter, within the common 3% guideline. It is 0.3" narrower.