265/40R20 vs 285/40R20

285/40R20 is 0.63 in (16.0 mm) taller than 265/40R20, a +2.22% diameter difference. With the speedometer set for 265/40R20, an indicated 60 mph is 61.3 mph on 285/40R20.

Is this a safe swap?

Diameter difference +2.22%: within the ±3% guideline

By overall diameter alone, 285/40R20 falls inside the ±3% range commonly used as a guideline when replacing 265/40R20. 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.

265/40R20 vs 285/40R20 differences
Measurement	265/40R20	285/40R20	Difference	% diff
Overall diameter	28.35 in (720.0 mm)	28.98 in (736.0 mm)	+0.63 in (+16.0 mm)	+2.22%
Sidewall height	4.17 in (106.0 mm)	4.49 in (114.0 mm)	+0.31 in (+8.0 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	89.05 in (2,261.9 mm)	91.03 in (2,312.2 mm)	+1.98 in (+50.3 mm)	+2.22%
Revolutions per mile	711	696	−15	−2.17%

True speed with the speedometer calibrated for 265/40R20
Indicated	Actual on 265/40R20	Actual on 285/40R20	Difference
30 mph	30.0 mph	30.7 mph	+0.7 mph
60 mph	60.0 mph	61.3 mph	+1.3 mph
75 mph	75.0 mph	76.7 mph	+1.7 mph

Ride-height change: 285/40R20 raises the vehicle by 0.31 in (8.0 mm) at the axle (half the +16.0 mm diameter difference).

285/40R20 is 0.63 in taller than 265/40R20 and 20 mm wider, a 2.22% difference in overall diameter.

With the speedometer calibrated for 265/40R20, an indicated 60 mph is actually 61.3 mph on 285/40R20, and revolutions per mile change from 711 to 696.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 265/40R20

Other comparisons with 285/40R20

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