Tire Ruler255/55R20 dimensions
| Overall diameter (height) | 31.04″ · 789 mm |
| Section width | 10.04″ · 255 mm |
| Sidewall height | 5.52″ · 140 mm |
| Wheel diameter | 20″ |
| Rim width (rule of thumb) | 7–9″ |
| Circumference | 97.5″ |
| Revolutions per mile | 650 |
| In inches (flotation style) | 31.0 × 10.0R20 |
How it’s calculated: the sidewall is 55% of the 255 mm width = 140.3 mm (5.52″). Add two sidewalls to the 20″ wheel: 20 + 2 × 5.52 = 31.04″.
Bigger tires than 255/55R20 on 20″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 245/60R20 | 31.6″ | +0.53″ (+1.7%) | 61.0 mph |
| 275/55R20 | 31.9″ | +0.87″ (+2.8%) | 61.7 mph |
| 305/50R20 | 32.0″ | +0.96″ (+3.1%) | 61.9 mph |
| 285/55R20 | 32.3″ | +1.30″ (+4.2%) | 62.5 mph |
| 265/60R20 | 32.5″ | +1.48″ (+4.8%) | 62.9 mph |
“60 mph reads” is your real speed when a speedometer set up for 255/55R20 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 255/55R20
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 |
|---|---|---|---|
| 285/50R20 | 31.2″ | 11.2″ | +0.6% |
| 275/50R20 | 30.8″ | 10.8″ | −0.7% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 31x10.50R15: 31.0″ tall on a 15″ wheel (−0.1%)
- 265/70R16: 30.6″ tall on a 16″ wheel (−1.4%)
- 255/70R17: 31.1″ tall on a 17″ wheel (+0.0%)
- 245/75R17: 31.5″ tall on a 17″ wheel (+1.4%)
- 275/65R17: 31.1″ tall on a 17″ wheel (+0.1%)
- 255/65R18: 31.1″ tall on an 18″ wheel (+0.0%)
- 275/60R18: 31.0″ tall on an 18″ wheel (−0.2%)
- 255/60R19: 31.0″ tall on a 19″ wheel (+0.0%)
- 275/45R21: 30.7″ tall on a 21″ wheel (−1.0%)
- 285/40R22: 31.0″ tall on a 22″ wheel (−0.2%)
Popular 255/55R20 comparisons
Frequently asked questions
Is 255/55R20 a 31 inch tire?
Yes. 255/55R20 is 31.04 inches tall, so it's sold and talked about as a 31-inch tire.
What size is 255/55R20 in inches?
255/55R20 is 31.0 inches tall (overall diameter), 10.0 inches wide, with a 5.5 inch sidewall, and fits a 20 inch wheel.
What tire size is equivalent to 255/55R20?
Sizes within 1.5% of the same diameter on a 20" wheel: 285/50R20 (31.2"), 275/50R20 (30.8"). Check load index and width before swapping.
What rim width fits 255/55R20?
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 255/55R20 make?
About 650 revolutions per mile in theory (circumference 97.5 in). Real tires turn slightly more because they flatten under load.