TireSizesFinder

265/50R20 vs 265/45R21

265/45R21 is 0.04 in (1.1 mm) shorter than 265/50R20, a −0.14% diameter difference. With the speedometer set for 265/50R20, an indicated 60 mph is 59.9 mph on 265/45R21.

Is this a safe swap?

Diameter difference −0.14%: under 1%

By overall diameter alone, 265/45R21 is a near match for 265/50R20; 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: 265/50R20 (30.43 in) vs 265/45R21 (30.39 in)265/50R2030.43 in × 10.43 in265/45R2130.39 in × 10.43 in
Side profile and tread width, drawn to the same scale.
265/50R20 vs 265/45R21 differences
Measurement265/50R20265/45R21Difference% diff
Overall diameter30.43 in (773.0 mm)30.39 in (771.9 mm)−0.04 in (−1.1 mm)−0.14%
Sidewall height5.22 in (132.5 mm)4.69 in (119.3 mm)−0.52 in (−13.2 mm)−10.00%
Section width10.43 in (265.0 mm)10.43 in (265.0 mm)0.00 in (0.0 mm)0.00%
Circumference95.61 in (2,428.5 mm)95.47 in (2,425.0 mm)−0.14 in (−3.5 mm)−0.14%
Revolutions per mile663664+1+0.14%
True speed with the speedometer calibrated for 265/50R20
IndicatedActual on 265/50R20Actual on 265/45R21Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.9 mph−0.1 mph

Ride-height change: 265/45R21 lowers the vehicle by 0.02 in (0.6 mm) at the axle (half the −1.1 mm diameter difference).

265/45R21 is 0.04 in shorter than 265/50R20 and the same width, a 0.14% difference in overall diameter.

With the speedometer calibrated for 265/50R20, an indicated 60 mph is actually 59.9 mph on 265/45R21, and revolutions per mile change from 663 to 664.

265/45R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 265/50R20.

Size pages

Other comparisons with 265/50R20

Other comparisons with 265/45R21

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