Tire Ruler255/50R20 dimensions
| Overall diameter (height) | 30.04″ · 763 mm |
| Section width | 10.04″ · 255 mm |
| Sidewall height | 5.02″ · 127 mm |
| Wheel diameter | 20″ |
| Rim width (rule of thumb) | 7–9″ |
| Circumference | 94.4″ |
| Revolutions per mile | 671 |
| In inches (flotation style) | 30.0 × 10.0R20 |
How it’s calculated: the sidewall is 50% of the 255 mm width = 127.5 mm (5.02″). Add two sidewalls to the 20″ wheel: 20 + 2 × 5.02 = 30.04″.
Bigger tires than 255/50R20 on 20″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 265/50R20 | 30.4″ | +0.39″ (+1.3%) | 60.8 mph |
| 275/50R20 | 30.8″ | +0.79″ (+2.6%) | 61.6 mph |
| 255/55R20 | 31.0″ | +1.00″ (+3.3%) | 62.0 mph |
| 285/50R20 | 31.2″ | +1.18″ (+3.9%) | 62.4 mph |
| 245/60R20 | 31.6″ | +1.54″ (+5.1%) | 63.1 mph |
“60 mph reads” is your real speed when a speedometer set up for 255/50R20 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 255/50R20
Within 1.5% of the same height on a 20″ wheel. Usually interchangeable for the speedometer; check width, load index and clearance.
| Size | Height | Width | Difference |
|---|---|---|---|
| 275/45R20 | 29.7″ | 10.8″ | −1.0% |
| 245/50R20 | 29.6″ | 9.6″ | −1.3% |
| 265/50R20 | 30.4″ | 10.4″ | +1.3% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 30x9.50R15: 30.0″ tall on a 15″ wheel (−0.1%)
- 245/75R16: 30.5″ tall on a 16″ wheel (+1.4%)
- 235/75R16: 29.9″ tall on a 16″ wheel (−0.5%)
- 255/70R16: 30.1″ tall on a 16″ wheel (+0.1%)
- 215/85R16: 30.4″ tall on a 16″ wheel (+1.2%)
- 255/65R17: 30.1″ tall on a 17″ wheel (+0.0%)
- 235/70R17: 30.0″ tall on a 17″ wheel (−0.3%)
- 235/65R18: 30.0″ tall on an 18″ wheel (−0.0%)
- 255/55R19: 30.0″ tall on a 19″ wheel (+0.0%)
- 245/55R19: 29.6″ tall on a 19″ wheel (−1.4%)
- 265/45R21: 30.4″ tall on a 21″ wheel (+1.2%)
- 265/40R22: 30.3″ tall on a 22″ wheel (+1.0%)
Popular 255/50R20 comparisons
Frequently asked questions
Is 255/50R20 a 30 inch tire?
Yes. 255/50R20 is 30.04 inches tall, so it's sold and talked about as a 30-inch tire.
What size is 255/50R20 in inches?
255/50R20 is 30.0 inches tall (overall diameter), 10.0 inches wide, with a 5.0 inch sidewall, and fits a 20 inch wheel.
What tire size is equivalent to 255/50R20?
Sizes within 1.5% of the same diameter on a 20" wheel: 275/45R20 (29.7"), 245/50R20 (29.6"), 265/50R20 (30.4"). Check load index and width before swapping.
What rim width fits 255/50R20?
As a rule of thumb, about 7–9 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 255/50R20 make?
About 671 revolutions per mile in theory (circumference 94.4 in). Real tires turn slightly more because they flatten under load.