265/45R21 vs 285/45R21

285/45R21 is 0.71 in (18.0 mm) taller than 265/45R21, a +2.33% diameter difference. With the speedometer set for 265/45R21, an indicated 60 mph is 61.4 mph on 285/45R21.

Is this a safe swap?

Diameter difference +2.33%: within the ±3% guideline

By overall diameter alone, 285/45R21 falls inside the ±3% range commonly used as a guideline when replacing 265/45R21. 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.

265/45R21 vs 285/45R21 differences
Measurement	265/45R21	285/45R21	Difference	% diff
Overall diameter	30.39 in (771.9 mm)	31.10 in (789.9 mm)	+0.71 in (+18.0 mm)	+2.33%
Sidewall height	4.69 in (119.3 mm)	5.05 in (128.3 mm)	+0.35 in (+9.0 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	95.47 in (2,425.0 mm)	97.70 in (2,481.5 mm)	+2.23 in (+56.5 mm)	+2.33%
Revolutions per mile	664	649	−15	−2.28%

True speed with the speedometer calibrated for 265/45R21
Indicated	Actual on 265/45R21	Actual on 285/45R21	Difference
30 mph	30.0 mph	30.7 mph	+0.7 mph
60 mph	60.0 mph	61.4 mph	+1.4 mph
75 mph	75.0 mph	76.7 mph	+1.7 mph

Ride-height change: 285/45R21 raises the vehicle by 0.35 in (9.0 mm) at the axle (half the +18.0 mm diameter difference).

285/45R21 is 0.71 in taller than 265/45R21 and 20 mm wider, a 2.33% difference in overall diameter.

With the speedometer calibrated for 265/45R21, an indicated 60 mph is actually 61.4 mph on 285/45R21, and revolutions per mile change from 664 to 649.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 265/45R21

Other comparisons with 285/45R21

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