Tire Ruler255/70R18 dimensions
| Overall diameter (height) | 32.06″ · 814 mm |
| Section width | 10.04″ · 255 mm |
| Sidewall height | 7.03″ · 179 mm |
| Wheel diameter | 18″ |
| Rim width (rule of thumb) | 7–9″ |
| Circumference | 100.7″ |
| Revolutions per mile | 629 |
| In inches (flotation style) | 32.1 × 10.0R18 |
How it’s calculated: the sidewall is 70% of the 255 mm width = 178.5 mm (7.03″). Add two sidewalls to the 18″ wheel: 18 + 2 × 7.03 = 32.06″.
Bigger tires than 255/70R18 on 18″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 285/65R18 | 32.6″ | +0.53″ (+1.7%) | 61.0 mph |
| 265/70R18 | 32.6″ | +0.55″ (+1.7%) | 61.0 mph |
| 33x12.50R18 | 33.0″ | +0.94″ (+2.9%) | 61.8 mph |
| 275/70R18 | 33.2″ | +1.10″ (+3.4%) | 62.1 mph |
| 295/70R18 | 34.3″ | +2.20″ (+6.9%) | 64.1 mph |
“60 mph reads” is your real speed when a speedometer set up for 255/70R18 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 255/70R18
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 |
|---|---|---|---|
| 275/65R18 | 32.1″ | 10.8″ | +0.1% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 32x11.50R15: 32.0″ tall on a 15″ wheel (−0.2%)
- 265/75R16: 31.6″ tall on a 16″ wheel (−1.3%)
- 235/85R16: 31.7″ tall on a 16″ wheel (−1.0%)
- 265/70R17: 31.6″ tall on a 17″ wheel (−1.4%)
- 275/70R17: 32.2″ tall on a 17″ wheel (+0.3%)
- 255/75R17: 32.1″ tall on a 17″ wheel (+0.0%)
- 275/55R20: 31.9″ tall on a 20″ wheel (−0.5%)
- 285/55R20: 32.3″ tall on a 20″ wheel (+0.9%)
- 265/60R20: 32.5″ tall on a 20″ wheel (+1.4%)
- 245/60R20: 31.6″ tall on a 20″ wheel (−1.5%)
- 305/50R20: 32.0″ tall on a 20″ wheel (−0.1%)
- 285/45R22: 32.1″ tall on a 22″ wheel (+0.1%)
- 275/45R22: 31.7″ tall on a 22″ wheel (−1.0%)
Popular 255/70R18 comparisons
Frequently asked questions
Is 255/70R18 a 32 inch tire?
Yes. 255/70R18 is 32.06 inches tall, so it's sold and talked about as a 32-inch tire.
What size is 255/70R18 in inches?
255/70R18 is 32.1 inches tall (overall diameter), 10.0 inches wide, with a 7.0 inch sidewall, and fits an 18 inch wheel.
What tire size is equivalent to 255/70R18?
Sizes within 1.5% of the same diameter on an 18" wheel: 275/65R18 (32.1"). Check load index and width before swapping.
What rim width fits 255/70R18?
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 255/70R18 make?
About 629 revolutions per mile in theory (circumference 100.7 in). Real tires turn slightly more because they flatten under load.