TireSizesFinder

265/45R20 vs 245/45R21

245/45R21 is 0.29 in (7.4 mm) taller than 265/45R20, a +0.99% diameter difference. With the speedometer set for 265/45R20, an indicated 60 mph is 60.6 mph on 245/45R21.

Is this a safe swap?

Diameter difference +0.99%: under 1%

By overall diameter alone, 245/45R21 is a near match for 265/45R20; 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: 265/45R20 (29.39 in) vs 245/45R21 (29.68 in)265/45R2029.39 in × 10.43 in245/45R2129.68 in × 9.65 in
Side profile and tread width, drawn to the same scale.
265/45R20 vs 245/45R21 differences
Measurement265/45R20245/45R21Difference% diff
Overall diameter29.39 in (746.5 mm)29.68 in (753.9 mm)+0.29 in (+7.4 mm)+0.99%
Sidewall height4.69 in (119.3 mm)4.34 in (110.3 mm)−0.35 in (−9.0 mm)−7.55%
Section width10.43 in (265.0 mm)9.65 in (245.0 mm)−0.79 in (−20.0 mm)−7.55%
Circumference92.33 in (2,345.2 mm)93.25 in (2,368.4 mm)+0.92 in (+23.2 mm)+0.99%
Revolutions per mile686679−7−0.98%
True speed with the speedometer calibrated for 265/45R20
IndicatedActual on 265/45R20Actual on 245/45R21Difference
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: 245/45R21 raises the vehicle by 0.15 in (3.7 mm) at the axle (half the +7.4 mm diameter difference).

245/45R21 is 0.29 in taller than 265/45R20 and 20 mm narrower, a 0.99% difference in overall diameter.

With the speedometer calibrated for 265/45R20, an indicated 60 mph is actually 60.6 mph on 245/45R21, and revolutions per mile change from 686 to 679.

245/45R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 265/45R20.

Size pages

Other comparisons with 265/45R20

Other comparisons with 245/45R21

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