285/55R20 vs 285/60R20 tire size
A 285/60R20 is 1.12 inches (29 mm) taller than a 285/55R20, and the same width. Fit them in place of 285/55R20 tires and the speedometer reads low: at 60 mph on it you’re doing 62.1 mph, 3.5% faster, and the vehicle sits 0.56 inches (14 mm) higher.
Sources checked
| Dimension | 285/55R20 | 285/60R20 | Change |
|---|---|---|---|
| Overall diameter | 32.34 in (822 mm) | 33.46 in (850 mm) | +1.12 in (+28 mm) |
| Section width | 11.22 in (285 mm) | 11.22 in (285 mm) | 0.00 in (0 mm) |
| Sidewall height | 6.17 in (157 mm) | 6.73 in (171 mm) | +0.56 in (+14 mm) |
| Aspect ratio | 55% | 60% | |
| Rim diameter | 20 in | 20 in | |
| Circumference | 101.6 in (2,581 mm) | 105.1 in (2,670 mm) | +3.5 in |
| Revolutions per mile | 624 | 603 | −21 |
| Revolutions per km | 387 | 374 | −13 |
Check another speed or size
Metric, LT and flotation
At 60 mph on the speedometer you’re doing
62.1mph
+3.5% · the speedometer reads low
- Height
- +1.12 in (+29 mm)
- Width
- 0.00 in (0 mm)
- Ground clearance
- +0.56 in (+14 mm)
- Each side, same wheel
- 0.00 in (0 mm)
285/55R20 and 285/60R20 side by side
| Dimension | 285/55R20 | 285/60R20 | Change |
|---|---|---|---|
| Overall diameter | 32.34 in (822 mm) | 33.46 in (850 mm) | +1.12 in (+28 mm) |
| Section width | 11.22 in (285 mm) | 11.22 in (285 mm) | 0.00 in (0 mm) |
| Sidewall height | 6.17 in (157 mm) | 6.73 in (171 mm) | +0.56 in (+14 mm) |
| Aspect ratio | 55% | 60% | |
| Rim diameter | 20 in | 20 in | |
| Circumference | 101.6 in | 105.1 in | +3.5 in |
| Revolutions per mile | 624 | 603 | −21 |
| Revolutions per km | 387 | 374 | −13 |
The working
- 285/55R20: sidewall = 285 mm × 55% = 156.8 mm = 6.17 in.
- Diameter = rim + 2 × sidewall = 20 + 2 × 6.17 = 32.34 in (822 mm).
- Circumference = π × 32.34 = 101.6 in; revolutions per mile = 63,360 ÷ 101.6 = 624.
- 285/60R20: sidewall = 285 mm × 60% = 171.0 mm = 6.73 in.
- Diameter = rim + 2 × sidewall = 20 + 2 × 6.73 = 33.46 in (850 mm).
- Circumference = π × 33.46 = 105.1 in; revolutions per mile = 63,360 ÷ 105.1 = 603.
- Speedometer. True speed = what it shows × new diameter ÷ old = 60 × 33.46 ÷ 32.34 = 62.1 mph.
- Ground clearance. Half the change in diameter: (33.46 − 32.34) ÷ 2 = +0.56 in.
Speedometer
A 285/60R20 turns 603 times a mile against the 285/55R20’s 624. With a speedometer set for 285/55R20, true speed is what it shows × 33.46 ÷ 32.34:
| Speedometer shows | True speed | Difference |
|---|---|---|
| 25 mph | 25.9 mph | +0.9 mph |
| 35 mph | 36.2 mph | +1.2 mph |
| 45 mph | 46.6 mph | +1.6 mph |
| 55 mph | 56.9 mph | +1.9 mph |
| 65 mph | 67.3 mph | +2.3 mph |
| 75 mph | 77.6 mph | +2.6 mph |
Clearance
- Ground clearance: +0.56 in (+14 mm), half the change in diameter.
- Top of the tread: +0.56 in (+14 mm), so that much less room under the fender.
- Each side, on the same wheel: no change.
A new wheel with a different width or offset moves the tire again. The sidewall goes from 6.17 to 6.73 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 | P285/55R20 | 32.4 in (+0.2%) | 11.7 in | 642 |
| Toyo Open Country A/T III | LT285/55R20 | 32.4 in (+0.2%) | 11.7 in | 642 |
| Nitto Trail Grappler M/T | LT285/55R20 | 32.6 in (+0.8%) | 11.69 in | – |
| Toyo Open Country A/T III | P285/60R20 | 33.5 in (+0.1%) | 11.5 in | 621 |
| Toyo Open Country A/T III | LT285/60R20 | 33.5 in (+0.1%) | 11.5 in | 621 |
| Nitto Trail Grappler M/T | LT285/60R20 | 33.7 in (+0.7%) | 11.5 in | – |
Each size on its own
- 285/55R20 tire size: 32.3 × 11.2 in
- 285/60R20 tire size: 33.5 × 11.2 in
Other comparisons
Questions
Can I fit 285/60R20 tires instead of 285/55R20?
They fit the same 20-inch wheels. A 285/60R20 is 1.12 inches (29 mm) taller than a 285/55R20, and the same width, so check three things first: that your wheels are within the 285/60R20’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 285/60R20 tires?
With a speedometer set for 285/55R20, the speedometer reads low: at 60 mph on it you’re doing 62.1 mph, 3.5% faster. The odometer is off the same way: over 1,000 miles driven it shows 966.5.
Does 285/60R20 change the ground clearance?
By +0.56 inches (+14 mm), half the change in diameter, at the axles and at the lowest point under them. The width doesn’t change.
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.