TireSizesFinder

245/55R20 vs 265/45R21

265/45R21 is 0.22 in (5.6 mm) shorter than 245/55R20, a −0.72% diameter difference. With the speedometer set for 245/55R20, an indicated 60 mph is 59.6 mph on 265/45R21.

Is this a safe swap?

Diameter difference −0.72%: under 1%

By overall diameter alone, 265/45R21 is a near match for 245/55R20; 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: 245/55R20 (30.61 in) vs 265/45R21 (30.39 in)245/55R2030.61 in × 9.65 in265/45R2130.39 in × 10.43 in
Side profile and tread width, drawn to the same scale.
245/55R20 vs 265/45R21 differences
Measurement245/55R20265/45R21Difference% diff
Overall diameter30.61 in (777.5 mm)30.39 in (771.9 mm)−0.22 in (−5.6 mm)−0.72%
Sidewall height5.31 in (134.8 mm)4.69 in (119.3 mm)−0.61 in (−15.5 mm)−11.50%
Section width9.65 in (245.0 mm)10.43 in (265.0 mm)+0.79 in (+20.0 mm)+8.16%
Circumference96.16 in (2,442.6 mm)95.47 in (2,425.0 mm)−0.69 in (−17.6 mm)−0.72%
Revolutions per mile659664+5+0.73%
True speed with the speedometer calibrated for 245/55R20
IndicatedActual on 245/55R20Actual on 265/45R21Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.6 mph−0.4 mph
75 mph75.0 mph74.5 mph−0.5 mph

Ride-height change: 265/45R21 lowers the vehicle by 0.11 in (2.8 mm) at the axle (half the −5.6 mm diameter difference).

265/45R21 is 0.22 in shorter than 245/55R20 and 20 mm wider, a 0.72% difference in overall diameter.

With the speedometer calibrated for 245/55R20, an indicated 60 mph is actually 59.6 mph on 265/45R21, and revolutions per mile change from 659 to 664.

265/45R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 245/55R20.

Size pages

Other comparisons with 245/55R20

Other comparisons with 265/45R21

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