TireSizesFinder

275/55R19 vs 255/50R21

255/50R21 is 0.13 in (3.3 mm) taller than 275/55R19, a +0.42% diameter difference. With the speedometer set for 275/55R19, an indicated 60 mph is 60.3 mph on 255/50R21.

Is this a safe swap?

Diameter difference +0.42%: under 1%

By overall diameter alone, 255/50R21 is a near match for 275/55R19; 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: 275/55R19 (30.91 in) vs 255/50R21 (31.04 in)275/55R1930.91 in × 10.83 in255/50R2131.04 in × 10.04 in
Side profile and tread width, drawn to the same scale.
275/55R19 vs 255/50R21 differences
Measurement275/55R19255/50R21Difference% diff
Overall diameter30.91 in (785.1 mm)31.04 in (788.4 mm)+0.13 in (+3.3 mm)+0.42%
Sidewall height5.95 in (151.3 mm)5.02 in (127.5 mm)−0.94 in (−23.7 mm)−15.70%
Section width10.83 in (275.0 mm)10.04 in (255.0 mm)−0.79 in (−20.0 mm)−7.27%
Circumference97.10 in (2,466.5 mm)97.51 in (2,476.8 mm)+0.41 in (+10.4 mm)+0.42%
Revolutions per mile652650−3−0.42%
True speed with the speedometer calibrated for 275/55R19
IndicatedActual on 275/55R19Actual on 255/50R21Difference
30 mph30.0 mph30.1 mph+0.1 mph
60 mph60.0 mph60.3 mph+0.3 mph
75 mph75.0 mph75.3 mph+0.3 mph

Ride-height change: 255/50R21 raises the vehicle by 0.06 in (1.7 mm) at the axle (half the +3.3 mm diameter difference).

255/50R21 is 0.13 in taller than 275/55R19 and 20 mm narrower, a 0.42% difference in overall diameter.

With the speedometer calibrated for 275/55R19, an indicated 60 mph is actually 60.3 mph on 255/50R21, and revolutions per mile change from 652 to 650.

255/50R21 mounts on a 21-inch wheel, a plus-2 fitment from the 19-inch wheel of 275/55R19.

Size pages

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