265/35R21 vs 285/35R21

285/35R21 is 0.55 in (14.0 mm) taller than 265/35R21, a +1.95% diameter difference. With the speedometer set for 265/35R21, an indicated 60 mph is 61.2 mph on 285/35R21.

Is this a safe swap?

Diameter difference +1.95%: within the ±3% guideline

By overall diameter alone, 285/35R21 falls inside the ±3% range commonly used as a guideline when replacing 265/35R21. 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.

265/35R21 vs 285/35R21 differences
Measurement	265/35R21	285/35R21	Difference	% diff
Overall diameter	28.30 in (718.9 mm)	28.85 in (732.9 mm)	+0.55 in (+14.0 mm)	+1.95%
Sidewall height	3.65 in (92.8 mm)	3.93 in (99.8 mm)	+0.28 in (+7.0 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	88.92 in (2,258.5 mm)	90.65 in (2,302.5 mm)	+1.73 in (+44.0 mm)	+1.95%
Revolutions per mile	713	699	−14	−1.91%

True speed with the speedometer calibrated for 265/35R21
Indicated	Actual on 265/35R21	Actual on 285/35R21	Difference
30 mph	30.0 mph	30.6 mph	+0.6 mph
60 mph	60.0 mph	61.2 mph	+1.2 mph
75 mph	75.0 mph	76.5 mph	+1.5 mph

Ride-height change: 285/35R21 raises the vehicle by 0.28 in (7.0 mm) at the axle (half the +14.0 mm diameter difference).

285/35R21 is 0.55 in taller than 265/35R21 and 20 mm wider, a 1.95% difference in overall diameter.

With the speedometer calibrated for 265/35R21, an indicated 60 mph is actually 61.2 mph on 285/35R21, and revolutions per mile change from 713 to 699.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 265/35R21

Other comparisons with 285/35R21

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