255/70R18 vs 265/70R18 tire size
A 265/70R18 is 0.55 inches (14 mm) taller and 0.39 inches (10 mm) wider than a 255/70R18. Fit them in place of 255/70R18 tires and the speedometer reads low: at 60 mph on it you’re doing 61.0 mph, 1.7% faster, and the vehicle sits 0.28 inches (7 mm) higher.
Sources checked
| Dimension | 255/70R18 | 265/70R18 | Change |
|---|---|---|---|
| Overall diameter | 32.06 in (814 mm) | 32.61 in (828 mm) | +0.55 in (+14 mm) |
| Section width | 10.04 in (255 mm) | 10.43 in (265 mm) | +0.39 in (+10 mm) |
| Sidewall height | 7.03 in (179 mm) | 7.30 in (186 mm) | +0.27 in (+7 mm) |
| Aspect ratio | 70% | 70% | |
| Rim diameter | 18 in | 18 in | |
| Circumference | 100.7 in (2,558 mm) | 102.4 in (2,602 mm) | +1.7 in |
| Revolutions per mile | 629 | 619 | −10 |
| Revolutions per km | 391 | 384 | −7 |
Check another speed or size
Metric, LT and flotation
At 60 mph on the speedometer you’re doing
61.0mph
+1.7% · the speedometer reads low
- Height
- +0.55 in (+14 mm)
- Width
- +0.39 in (+10 mm)
- Ground clearance
- +0.28 in (+7 mm)
- Each side, same wheel
- +0.20 in (+5 mm)
255/70R18 and 265/70R18 side by side
| Dimension | 255/70R18 | 265/70R18 | Change |
|---|---|---|---|
| Overall diameter | 32.06 in (814 mm) | 32.61 in (828 mm) | +0.55 in (+14 mm) |
| Section width | 10.04 in (255 mm) | 10.43 in (265 mm) | +0.39 in (+10 mm) |
| Sidewall height | 7.03 in (179 mm) | 7.30 in (186 mm) | +0.27 in (+7 mm) |
| Aspect ratio | 70% | 70% | |
| Rim diameter | 18 in | 18 in | |
| Circumference | 100.7 in | 102.4 in | +1.7 in |
| Revolutions per mile | 629 | 619 | −10 |
| Revolutions per km | 391 | 384 | −7 |
The working
- 255/70R18: sidewall = 255 mm × 70% = 178.5 mm = 7.03 in.
- Diameter = rim + 2 × sidewall = 18 + 2 × 7.03 = 32.06 in (814 mm).
- Circumference = π × 32.06 = 100.7 in; revolutions per mile = 63,360 ÷ 100.7 = 629.
- 265/70R18: sidewall = 265 mm × 70% = 185.5 mm = 7.30 in.
- Diameter = rim + 2 × sidewall = 18 + 2 × 7.30 = 32.61 in (828 mm).
- Circumference = π × 32.61 = 102.4 in; revolutions per mile = 63,360 ÷ 102.4 = 619.
- Speedometer. True speed = what it shows × new diameter ÷ old = 60 × 32.61 ÷ 32.06 = 61.0 mph.
- Ground clearance. Half the change in diameter: (32.61 − 32.06) ÷ 2 = +0.28 in.
Speedometer
A 265/70R18 turns 619 times a mile against the 255/70R18’s 629. With a speedometer set for 255/70R18, true speed is what it shows × 32.61 ÷ 32.06:
| Speedometer shows | True speed | Difference |
|---|---|---|
| 25 mph | 25.4 mph | +0.4 mph |
| 35 mph | 35.6 mph | +0.6 mph |
| 45 mph | 45.8 mph | +0.8 mph |
| 55 mph | 55.9 mph | +0.9 mph |
| 65 mph | 66.1 mph | +1.1 mph |
| 75 mph | 76.3 mph | +1.3 mph |
Clearance
- Ground clearance: +0.28 in (+7 mm), half the change in diameter.
- Top of the tread: +0.28 in (+7 mm), so that much less room under the fender.
- Each side, on the same wheel: +0.20 in (+5 mm), toward the suspension inside and toward the fender lip outside.
A new wheel with a different width or offset moves the tire again. The sidewall goes from 7.03 to 7.30 inches.
What tire makers publish
Inflated on the maker’s measuring rim; the percentage is against the arithmetic.
| Tire | Size as printed | Diameter | Width | Revs per mile |
|---|---|---|---|---|
| Toyo Open Country A/T III | 255/70R18 | 32.1 in (+0.1%) | 10.2 in | 647 |
| Toyo Open Country A/T III | 265/70R18 | 32.6 in (0.0%) | 10.7 in | 636 |
| Toyo Open Country A/T III | LT265/70R18 | 32.6 in (0.0%) | 10.7 in | 636 |
Each size on its own
- 255/70R18 tire size: 32.1 × 10.0 in
- 265/70R18 tire size: 32.6 × 10.4 in
Other comparisons
Questions
Can I fit 265/70R18 tires instead of 255/70R18?
They fit the same 18-inch wheels. A 265/70R18 is 0.55 inches (14 mm) taller and 0.39 inches (10 mm) wider than a 255/70R18, so check three things first: that your wheels are within the 265/70R18’s approved rim width range, which tire makers list for each size; that it clears the fenders and suspension at full lock and full travel; and that its load index meets what your door-jamb placard asks for.
How far off is the speedometer with 265/70R18 tires?
With a speedometer set for 255/70R18, the speedometer reads low: at 60 mph on it you’re doing 61.0 mph, 1.7% faster. The odometer is off the same way: over 1,000 miles driven it shows 983.1.
Does 265/70R18 change the ground clearance?
By +0.28 inches (+7 mm), half the change in diameter, at the axles and at the lowest point under them. On the same wheel, each sidewall sits 0.20 inches further out, inside and outside.
Sources
- Bridgestone Americas: Determining tire size: P-metric, Euro-metric, LT-metric, C-type and flotation sizes, and what each number means (checked October 28, 2026)
- Toyo Tires: Extensa A/S II sizes and specifications: inflated overall diameter and width, revolutions per mile (checked October 28, 2026)
- Toyo Tires: Proxes Sport A/S sizes and specifications: inflated overall diameter and width, revolutions per mile (checked October 28, 2026)
- Toyo Tires: Open Country A/T III sizes and specifications: P-metric, LT-metric and flotation sizes, with revolutions per mile (checked October 28, 2026)
- Nitto Tire: Trail Grappler M/T sizes and specs: inflated overall diameter and width, LT-metric and flotation sizes (checked October 28, 2026)
Spotted a number that doesn’t match your manual or a source? Tell us; corrections are logged on the sources page.