285/50R20 vs 265/55R20

265/55R20 is 0.26 in (6.5 mm) taller than 285/50R20, a +0.82% diameter difference. With the speedometer set for 285/50R20, an indicated 60 mph is 60.5 mph on 265/55R20.

Is this a safe swap?

Diameter difference +0.82%: under 1%

By overall diameter alone, 265/55R20 is a near match for 285/50R20; the speedometer changes by less than 1%. 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.

285/50R20 vs 265/55R20 differences
Measurement	285/50R20	265/55R20	Difference	% diff
Overall diameter	31.22 in (793.0 mm)	31.48 in (799.5 mm)	+0.26 in (+6.5 mm)	+0.82%
Sidewall height	5.61 in (142.5 mm)	5.74 in (145.8 mm)	+0.13 in (+3.3 mm)	+2.28%
Section width	11.22 in (285.0 mm)	10.43 in (265.0 mm)	−0.79 in (−20.0 mm)	−7.02%
Circumference	98.08 in (2,491.3 mm)	98.89 in (2,511.7 mm)	+0.80 in (+20.4 mm)	+0.82%
Revolutions per mile	646	641	−5	−0.81%

True speed with the speedometer calibrated for 285/50R20
Indicated	Actual on 285/50R20	Actual on 265/55R20	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 265/55R20 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

265/55R20 is 0.26 in taller than 285/50R20 and 20 mm narrower, a 0.82% difference in overall diameter.

With the speedometer calibrated for 285/50R20, an indicated 60 mph is actually 60.5 mph on 265/55R20, and revolutions per mile change from 646 to 641.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 285/50R20

Other comparisons with 265/55R20

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