265/55R20 vs 285/55R20

285/55R20 is 0.87 in (22.0 mm) taller than 265/55R20, a +2.75% diameter difference. With the speedometer set for 265/55R20, an indicated 60 mph is 61.7 mph on 285/55R20.

Is this a safe swap?

Diameter difference +2.75%: within the ±3% guideline

By overall diameter alone, 285/55R20 falls inside the ±3% range commonly used as a guideline when replacing 265/55R20. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

265/55R20 vs 285/55R20 differences
Measurement	265/55R20	285/55R20	Difference	% diff
Overall diameter	31.48 in (799.5 mm)	32.34 in (821.5 mm)	+0.87 in (+22.0 mm)	+2.75%
Sidewall height	5.74 in (145.8 mm)	6.17 in (156.8 mm)	+0.43 in (+11.0 mm)	+7.55%
Section width	10.43 in (265.0 mm)	11.22 in (285.0 mm)	+0.79 in (+20.0 mm)	+7.55%
Circumference	98.89 in (2,511.7 mm)	101.61 in (2,580.8 mm)	+2.72 in (+69.1 mm)	+2.75%
Revolutions per mile	641	624	−17	−2.68%

True speed with the speedometer calibrated for 265/55R20
Indicated	Actual on 265/55R20	Actual on 285/55R20	Difference
30 mph	30.0 mph	30.8 mph	+0.8 mph
60 mph	60.0 mph	61.7 mph	+1.7 mph
75 mph	75.0 mph	77.1 mph	+2.1 mph

Ride-height change: 285/55R20 raises the vehicle by 0.43 in (11.0 mm) at the axle (half the +22.0 mm diameter difference).

285/55R20 is 0.87 in taller than 265/55R20 and 20 mm wider, a 2.75% difference in overall diameter.

With the speedometer calibrated for 265/55R20, an indicated 60 mph is actually 61.7 mph on 285/55R20, and revolutions per mile change from 641 to 624.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 265/55R20

Other comparisons with 285/55R20

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.