TireSizesFinder

275/50R19 vs 255/45R21

255/45R21 is 0.21 in (5.3 mm) taller than 275/50R19, a +0.70% diameter difference. With the speedometer set for 275/50R19, an indicated 60 mph is 60.4 mph on 255/45R21.

Is this a safe swap?

Diameter difference +0.70%: under 1%

By overall diameter alone, 255/45R21 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 255/45R21 (30.04 in)275/50R1929.83 in × 10.83 in255/45R2130.04 in × 10.04 in
Side profile and tread width, drawn to the same scale.
275/50R19 vs 255/45R21 differences
Measurement275/50R19255/45R21Difference% diff
Overall diameter29.83 in (757.6 mm)30.04 in (762.9 mm)+0.21 in (+5.3 mm)+0.70%
Sidewall height5.41 in (137.5 mm)4.52 in (114.8 mm)−0.90 in (−22.7 mm)−16.55%
Section width10.83 in (275.0 mm)10.04 in (255.0 mm)−0.79 in (−20.0 mm)−7.27%
Circumference93.70 in (2,380.1 mm)94.36 in (2,396.7 mm)+0.66 in (+16.7 mm)+0.70%
Revolutions per mile676671−5−0.69%
True speed with the speedometer calibrated for 275/50R19
IndicatedActual on 275/50R19Actual on 255/45R21Difference
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: 255/45R21 raises the vehicle by 0.10 in (2.7 mm) at the axle (half the +5.3 mm diameter difference).

255/45R21 is 0.21 in taller than 275/50R19 and 20 mm narrower, a 0.70% difference in overall diameter.

With the speedometer calibrated for 275/50R19, an indicated 60 mph is actually 60.4 mph on 255/45R21, and revolutions per mile change from 676 to 671.

255/45R21 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.