Data sheet TS-C11 · Comparison
275/65R20 vs 285/65R20
285/65R20 is nominally 0.51 in taller than 275/65R20, a 1.5% diameter increase by the formula. It is also wider, with more sidewall height and fewer revolutions per mile.
Fig. 1 — Cross-section, size 2
Table 1 — Data
285/65R20 is 34.59″ tall, +1.50% against 275/65R20. At 60 mph on the dial you drive 60.9 mph.
| Item | 275/65R20 | 285/65R20 | Change |
|---|---|---|---|
| DOverall diameter | 34.07″ | 34.59″ | +1.50% |
| ASection width | 10.83″ | 11.22″ | +0.39″ |
| BSidewall | 7.04″ | 7.29″ | +0.26″ |
| CRim | 20″ | 20″ | same |
| Revs per mile | 592 | 583 | −9 |
| Dial 60 mph = | 60.0 | 60.9 | +1.5% |
| Axle height | 17.04″ | 17.29″ | +0.26″ |
+1.50% — within the ±3% rule of thumb tire shops use. The speedometer and gearing stay close to stock.
Where to buy 285/65R20 ↓Fig. 2
Side view and width, to scale
Size 1 dashed, size 2 solid, on one ground line.
275/65R20285/65R20
Table 2 — Speedometer
| Dial shows | True speed | Difference |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 |
| 45 mph | 45.7 mph | +0.7 |
| 60 mph | 60.9 mph | +0.9 |
| 70 mph | 71.1 mph | +1.1 |
| 80 mph | 81.2 mph | +1.2 |
Engine RPM at the same road speed: −1.5%. Gear ratio calculator
Table 3
Published dimensions
From each maker’s size table. A tire is listed only with a source.
The math says 34.59″. 9 tires from 5 makers measure 34.57″–34.80″. Tallest here: Nitto Ridge Grappler (hybrid terrain), 34.80″. Check the maker’s number before you buy for a tight fit.
| Tire | Type | Diameter | Width | Rims, in | Weight | Tread | Max load |
|---|---|---|---|---|---|---|---|
| Nitto Recon Grappler A/Tnittotire.com · Oct 15, 2026 | LT · E 127/124S | 34.57″ | 11.50″ | 8.5–10.0 | 60.3 lb | 16.0/32″ | 3,860 lb @ 80 psi |
| Nitto Terra Grappler G3nittotire.com · Oct 15, 2026 | LT · E 127/124S | 34.57″ | 11.50″ | 8.5–10.0 | 59.5 lb | 16.0/32″ | 3,860 lb @ 80 psi |
| Firestone Destination X/Tfirestonetire.com · Oct 15, 2026 | LT · E 127S | 34.60″ | — | 8.0–10.0 | 53.3 lb | 16.0/32″ | — |
| Kumho Road Venture AT52kumhotireusa.com · Oct 15, 2026 | LT · E 127/124S | 34.60″ | 11.50″ | 8.5–10.0 | 59.3 lb | 16.0/32″ | 3,860 lb @ 80 psi |
| Mickey Thompson Baja Boss A/Tmickeythompsontires.com · Oct 15, 2026 | LT · E 127Q | 34.60″ | 11.50″ | 8.0–10.0 | 69.0 lb | 18.5/32″ | 3,860 lb @ 80 psi |
| Toyo Open Country A/T IIItoyotires.com · Oct 15, 2026 | LT · E 127/124S | 34.60″ | 11.50″ | 8.5–10.0 | 56.0 lb | 16.5/32″ | 3,860 lb @ 80 psi |
| Toyo Open Country R/T Trailtoyotires.com · Oct 15, 2026 | LT · E 127/124R | 34.60″ | 11.50″ | 8.5–10.0 | 61.0 lb | 16.5/32″ | 3,860 lb @ 80 psi |
| Toyo Open Country H/T IItoyotires.com · Oct 15, 2026 | LT · E 127/124R | 34.60″ | 11.50″ | 8.0–10.0 | 60.0 lb | 15.8/32″ | 3,860 lb @ 80 psi |
| Nitto Ridge Grapplernittotire.com · Oct 15, 2026 | LT · E 127/124Q | 34.80″ | 11.50″ | 8.5–10.0 | 63.7 lb | 16.4/32″ | 3,860 lb @ 80 psi |
§ 1
How much taller and wider?
By the formula, diameter increases from 34.1 in (866 mm) to 34.6 in (879 mm). Section width increases from 10.8 in to 11.2 in (+10 mm), while sidewall height increases from 7.0 in to 7.3 in.
Nominal revolutions per mile drop from 592 to 583. Ground clearance at the axle increases by 0.26 in (7 mm). These are unloaded nominal measurements; actual tires measure differently.
§ 2
How do speed and gearing change?
After changing to 285/65R20, the nominal speedometer calculation gives 60.9 mph true at 60 mph indicated. At 100 km/h indicated, true speed is 101.5 km/h. Actual distance traveled is also 1.5% greater than the odometer indicates.
By the formula, at 65 mph with a 3.73 axle ratio and a 1.00 transmission gear, engine speed drops from 2,392 rpm to 2,356 rpm. The calculated axle ratio that restores the original engine speed is 3.79: 3.73 × 34.59 / 34.07. The gear ratio calculator describes this mathematical relationship, not a modification recommendation.
§ 3
What do maker tables list?
The checked size tables from Nitto, Firestone, Kumho, Toyo and Mickey Thompson list 22 tires in 275/65R20: 18 LT and 4 passenger versions. Published diameters span 34.05 in to 34.7 in, with SL and E load ranges represented.
Those makers list 9 tires in 285/65R20, all LT load range E. Published diameters span 34.57 in to 34.8 in. Toyo lists 609 revs per mile for its Open Country A/T III in LT275/65R20 and 601 in LT285/65R20, distinct from the nominal calculations.
§ 4
What are the practical trade-offs?
The taller 285/65R20 adds nominal axle clearance and lowers engine rpm at the same road speed. Its greater diameter and width also require more room around the tire.
The shorter, narrower 275/65R20 has smaller nominal dimensions, but the published diameter ranges overlap. Compare the specific models and their approved rim widths, not just the size labels. Fit depends on the vehicle, wheels and suspension.
Table 4
Sizes within 3% of 285/65R20
Same rim or ±1″, diameter within 3%. A shop rule of thumb, not a law.
| Size | Diameter | Width | vs 285/65R20 | At 60 mph | Clearance |
|---|---|---|---|---|---|
| 315/60R20 | 34.88″ | 12.4″ | +0.9% | 60.5 | +0.15″ |
| 35x11.50R20 | 35.00″ | 11.5″ | +1.2% | 60.7 | +0.21″ |
| 35x12.50R20 | 35.00″ | 12.5″ | +1.2% | 60.7 | +0.21″ |
| 35x13.50R20 | 35.00″ | 13.5″ | +1.2% | 60.7 | +0.21″ |
| 35x15.50R20 | 35.00″ | 15.5″ | +1.2% | 60.7 | +0.21″ |
| 295/65R20 | 35.10″ | 11.6″ | +1.5% | 60.9 | +0.26″ |
| 275/65R20 | 34.07″ | 10.8″ | −1.5% | 59.1 | −0.26″ |
| 34x11.50R20 | 34.00″ | 11.5″ | −1.7% | 59.0 | −0.29″ |
| 295/60R20 | 33.94″ | 11.6″ | −1.9% | 58.9 | −0.32″ |
| 325/60R20 | 35.35″ | 12.8″ | +2.2% | 61.3 | +0.38″ |
Size sheets
Q&A
Common questions
Is 285/65R20 within 3% of 275/65R20?
Yes. The nominal increase is 1.5%, inside the ±3% diameter window. That window is a tire-shop rule of thumb, not a law or vehicle maker specification.
Do both sizes use the same approved rim widths?
Not necessarily. Toyo lists 8.0–9.5 in for the Open Country A/T III in LT275/65R20 and 8.5–10.0 in for LT285/65R20.
Is every 285/65R20 taller than every 275/65R20?
No. The checked maker tables show overlapping diameter ranges: 34.05–34.7 in for 275/65R20 and 34.57–34.8 in for 285/65R20.
Notes
Method and sources
Each number and rule comes from a source with the date it was checked.
- Sidewall = width × aspect ratio ÷ 100
- Diameter = rim × 25.4 + 2 × sidewall (mm)
- Revs per mile = 63,360 ÷ (π × diameter, in)
- True speed = dial × new diameter ÷ old diameter
- Clearance change = half the diameter change
Numbers are nominal: the tire unloaded, on its measuring rim. Revs per mile published by makers run higher than the formula. “Within 3%” is a rule of thumb tire shops use, not a law. Tire pressure: the placard on your door jamb.
- Toyo: size table (toyotires.com)checked Oct 15, 2026
Related
Calculators and size classes
- Tire size calculatorTwo sizes: diameter, sidewall, revs and speedometer.
- Compare up to 4 sizesUp to four sizes side by side, drawn to scale.
- Metric ↔ inchesMetric to inches, and 33x12.50R20 to metric.
- Speedometer errorTrue speed after a size change.
- Gear ratio and RPMEngine RPM and the ratio to regear to.
- Wheel offset and pokeBackspacing, poke and inner clearance.
- DOT date codeHow old a tire is, from the DOT number.
- Load index chartLoad index in pounds and kilograms.
- Bolt patternMeasure it, convert inches to mm.
- Rim size and tire fitWhat 17x8 ET35 means, which sizes go on it.
- What fits my carStart from the placard on the door.
- Tire size chartCommon sizes in inches, by rim.