TireSizesFinder

255/50R19 vs 235/45R21

235/45R21 is 0.29 in (7.3 mm) taller than 255/50R19, a +0.99% diameter difference. With the speedometer set for 255/50R19, an indicated 60 mph is 60.6 mph on 235/45R21.

Is this a safe swap?

Diameter difference +0.99%: under 1%

By overall diameter alone, 235/45R21 is a near match for 255/50R19; 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: 255/50R19 (29.04 in) vs 235/45R21 (29.33 in)255/50R1929.04 in × 10.04 in235/45R2129.33 in × 9.25 in
Side profile and tread width, drawn to the same scale.
255/50R19 vs 235/45R21 differences
Measurement255/50R19235/45R21Difference% diff
Overall diameter29.04 in (737.6 mm)29.33 in (744.9 mm)+0.29 in (+7.3 mm)+0.99%
Sidewall height5.02 in (127.5 mm)4.16 in (105.8 mm)−0.86 in (−21.7 mm)−17.06%
Section width10.04 in (255.0 mm)9.25 in (235.0 mm)−0.79 in (−20.0 mm)−7.84%
Circumference91.23 in (2,317.2 mm)92.13 in (2,340.2 mm)+0.90 in (+22.9 mm)+0.99%
Revolutions per mile695688−7−0.98%
True speed with the speedometer calibrated for 255/50R19
IndicatedActual on 255/50R19Actual on 235/45R21Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.6 mph+0.6 mph
75 mph75.0 mph75.7 mph+0.7 mph

Ride-height change: 235/45R21 raises the vehicle by 0.14 in (3.7 mm) at the axle (half the +7.3 mm diameter difference).

235/45R21 is 0.29 in taller than 255/50R19 and 20 mm narrower, a 0.99% difference in overall diameter.

With the speedometer calibrated for 255/50R19, an indicated 60 mph is actually 60.6 mph on 235/45R21, and revolutions per mile change from 695 to 688.

235/45R21 mounts on a 21-inch wheel, a plus-2 fitment from the 19-inch wheel of 255/50R19.

Size pages

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