TireSizesFinder

275/50R19 vs 245/45R21

245/45R21 is 0.15 in (3.7 mm) shorter than 275/50R19, a −0.49% diameter difference. With the speedometer set for 275/50R19, an indicated 60 mph is 59.7 mph on 245/45R21.

Is this a safe swap?

Diameter difference −0.49%: under 1%

By overall diameter alone, 245/45R21 is a near match for 275/50R19; 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: 275/50R19 (29.83 in) vs 245/45R21 (29.68 in)275/50R1929.83 in × 10.83 in245/45R2129.68 in × 9.65 in
Side profile and tread width, drawn to the same scale.
275/50R19 vs 245/45R21 differences
Measurement275/50R19245/45R21Difference% diff
Overall diameter29.83 in (757.6 mm)29.68 in (753.9 mm)−0.15 in (−3.7 mm)−0.49%
Sidewall height5.41 in (137.5 mm)4.34 in (110.3 mm)−1.07 in (−27.2 mm)−19.82%
Section width10.83 in (275.0 mm)9.65 in (245.0 mm)−1.18 in (−30.0 mm)−10.91%
Circumference93.70 in (2,380.1 mm)93.25 in (2,368.4 mm)−0.46 in (−11.6 mm)−0.49%
Revolutions per mile676679+3+0.49%
True speed with the speedometer calibrated for 275/50R19
IndicatedActual on 275/50R19Actual on 245/45R21Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.7 mph−0.3 mph
75 mph75.0 mph74.6 mph−0.4 mph

Ride-height change: 245/45R21 lowers the vehicle by 0.07 in (1.8 mm) at the axle (half the −3.7 mm diameter difference).

245/45R21 is 0.15 in shorter than 275/50R19 and 30 mm narrower, a 0.49% difference in overall diameter.

With the speedometer calibrated for 275/50R19, an indicated 60 mph is actually 59.7 mph on 245/45R21, and revolutions per mile change from 676 to 679.

245/45R21 mounts on a 21-inch wheel, a plus-2 fitment from the 19-inch wheel of 275/50R19.

Size pages

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