Tire Ruler255/65R18 dimensions
| Overall diameter (height) | 31.05″ · 789 mm |
| Section width | 10.04″ · 255 mm |
| Sidewall height | 6.53″ · 166 mm |
| Wheel diameter | 18″ |
| Rim width (rule of thumb) | 7–9″ |
| Circumference | 97.6″ |
| Revolutions per mile | 650 |
| In inches (flotation style) | 31.1 × 10.0R18 |
How it’s calculated: the sidewall is 65% of the 255 mm width = 165.8 mm (6.53″). Add two sidewalls to the 18″ wheel: 18 + 2 × 6.53 = 31.05″.
Bigger tires than 255/65R18 on 18″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 265/65R18 | 31.6″ | +0.51″ (+1.6%) | 61.0 mph |
| 255/70R18 | 32.1″ | +1.00″ (+3.2%) | 61.9 mph |
| 275/65R18 | 32.1″ | +1.02″ (+3.3%) | 62.0 mph |
| 285/65R18 | 32.6″ | +1.54″ (+4.9%) | 63.0 mph |
| 265/70R18 | 32.6″ | +1.56″ (+5.0%) | 63.0 mph |
“60 mph reads” is your real speed when a speedometer set up for 255/65R18 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 255/65R18
Within 1.5% of the same height on an 18″ wheel. Usually interchangeable for the speedometer; check width, load index and clearance.
| Size | Height | Width | Difference |
|---|---|---|---|
| 275/60R18 | 31.0″ | 10.8″ | −0.2% |
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 (−0.2%)
- 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 (+1.3%)
- 275/65R17: 31.1″ tall on a 17″ wheel (+0.1%)
- 255/60R19: 31.0″ tall on a 19″ wheel (−0.0%)
- 255/55R20: 31.0″ tall on a 20″ wheel (−0.0%)
- 285/50R20: 31.2″ tall on a 20″ wheel (+0.5%)
- 275/50R20: 30.8″ tall on a 20″ wheel (−0.7%)
- 275/45R21: 30.7″ tall on a 21″ wheel (−1.0%)
- 285/40R22: 31.0″ tall on a 22″ wheel (−0.2%)
Popular 255/65R18 comparisons
Frequently asked questions
Is 255/65R18 a 31 inch tire?
Yes. 255/65R18 is 31.05 inches tall, so it's sold and talked about as a 31-inch tire.
What size is 255/65R18 in inches?
255/65R18 is 31.1 inches tall (overall diameter), 10.0 inches wide, with a 6.5 inch sidewall, and fits an 18 inch wheel.
What tire size is equivalent to 255/65R18?
Sizes within 1.5% of the same diameter on an 18" wheel: 275/60R18 (31.0"). Check load index and width before swapping.
What rim width fits 255/65R18?
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 255/65R18 make?
About 650 revolutions per mile in theory (circumference 97.6 in). Real tires turn slightly more because they flatten under load.