TireSizesFinder

235/55R20 vs 265/45R21

265/45R21 is 0.21 in (5.4 mm) taller than 235/55R20, a +0.70% diameter difference. With the speedometer set for 235/55R20, an indicated 60 mph is 60.4 mph on 265/45R21.

Is this a safe swap?

Diameter difference +0.70%: under 1%

By overall diameter alone, 265/45R21 is a near match for 235/55R20; 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: 235/55R20 (30.18 in) vs 265/45R21 (30.39 in)235/55R2030.18 in × 9.25 in265/45R2130.39 in × 10.43 in
Side profile and tread width, drawn to the same scale.
235/55R20 vs 265/45R21 differences
Measurement235/55R20265/45R21Difference% diff
Overall diameter30.18 in (766.5 mm)30.39 in (771.9 mm)+0.21 in (+5.4 mm)+0.70%
Sidewall height5.09 in (129.3 mm)4.69 in (119.3 mm)−0.39 in (−10.0 mm)−7.74%
Section width9.25 in (235.0 mm)10.43 in (265.0 mm)+1.18 in (+30.0 mm)+12.77%
Circumference94.80 in (2,408.0 mm)95.47 in (2,425.0 mm)+0.67 in (+17.0 mm)+0.70%
Revolutions per mile668664−5−0.70%
True speed with the speedometer calibrated for 235/55R20
IndicatedActual on 235/55R20Actual on 265/45R21Difference
30 mph30.0 mph30.2 mph+0.2 mph
60 mph60.0 mph60.4 mph+0.4 mph
75 mph75.0 mph75.5 mph+0.5 mph

Ride-height change: 265/45R21 raises the vehicle by 0.11 in (2.7 mm) at the axle (half the +5.4 mm diameter difference).

265/45R21 is 0.21 in taller than 235/55R20 and 30 mm wider, a 0.70% difference in overall diameter.

With the speedometer calibrated for 235/55R20, an indicated 60 mph is actually 60.4 mph on 265/45R21, and revolutions per mile change from 668 to 664.

265/45R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 235/55R20.

Size pages

Other comparisons with 235/55R20

Other comparisons with 265/45R21

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