TireSizesFinder

285/45R20 vs 265/45R21

265/45R21 is 0.29 in (7.4 mm) taller than 285/45R20, a +0.97% diameter difference. With the speedometer set for 285/45R20, an indicated 60 mph is 60.6 mph on 265/45R21.

Is this a safe swap?

Diameter difference +0.97%: under 1%

By overall diameter alone, 265/45R21 is a near match for 285/45R20; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 285/45R20 (30.10 in) vs 265/45R21 (30.39 in)285/45R2030.10 in × 11.22 in265/45R2130.39 in × 10.43 in
Side profile and tread width, drawn to the same scale.
285/45R20 vs 265/45R21 differences
Measurement285/45R20265/45R21Difference% diff
Overall diameter30.10 in (764.5 mm)30.39 in (771.9 mm)+0.29 in (+7.4 mm)+0.97%
Sidewall height5.05 in (128.3 mm)4.69 in (119.3 mm)−0.35 in (−9.0 mm)−7.02%
Section width11.22 in (285.0 mm)10.43 in (265.0 mm)−0.79 in (−20.0 mm)−7.02%
Circumference94.56 in (2,401.7 mm)95.47 in (2,425.0 mm)+0.92 in (+23.2 mm)+0.97%
Revolutions per mile670664−6−0.96%
True speed with the speedometer calibrated for 285/45R20
IndicatedActual on 285/45R20Actual on 265/45R21Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.6 mph+0.6 mph
75 mph75.0 mph75.7 mph+0.7 mph

Ride-height change: 265/45R21 raises the vehicle by 0.15 in (3.7 mm) at the axle (half the +7.4 mm diameter difference).

265/45R21 is 0.29 in taller than 285/45R20 and 20 mm narrower, a 0.97% difference in overall diameter.

With the speedometer calibrated for 285/45R20, an indicated 60 mph is actually 60.6 mph on 265/45R21, and revolutions per mile change from 670 to 664.

265/45R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 285/45R20.

Size pages

Other comparisons with 285/45R20

Other comparisons with 265/45R21

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.