TireSizesFinder

245/55R19 vs 235/45R21

235/45R21 is 0.28 in (7.2 mm) shorter than 245/55R19, a −0.96% diameter difference. With the speedometer set for 245/55R19, an indicated 60 mph is 59.4 mph on 235/45R21.

Is this a safe swap?

Diameter difference −0.96%: under 1%

By overall diameter alone, 235/45R21 is a near match for 245/55R19; 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: 245/55R19 (29.61 in) vs 235/45R21 (29.33 in)245/55R1929.61 in × 9.65 in235/45R2129.33 in × 9.25 in
Side profile and tread width, drawn to the same scale.
245/55R19 vs 235/45R21 differences
Measurement245/55R19235/45R21Difference% diff
Overall diameter29.61 in (752.1 mm)29.33 in (744.9 mm)−0.28 in (−7.2 mm)−0.96%
Sidewall height5.31 in (134.8 mm)4.16 in (105.8 mm)−1.14 in (−29.0 mm)−21.52%
Section width9.65 in (245.0 mm)9.25 in (235.0 mm)−0.39 in (−10.0 mm)−4.08%
Circumference93.02 in (2,362.8 mm)92.13 in (2,340.2 mm)−0.89 in (−22.6 mm)−0.96%
Revolutions per mile681688+7+0.97%
True speed with the speedometer calibrated for 245/55R19
IndicatedActual on 245/55R19Actual on 235/45R21Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.3 mph−0.7 mph

Ride-height change: 235/45R21 lowers the vehicle by 0.14 in (3.6 mm) at the axle (half the −7.2 mm diameter difference).

235/45R21 is 0.28 in shorter than 245/55R19 and 10 mm narrower, a 0.96% difference in overall diameter.

With the speedometer calibrated for 245/55R19, an indicated 60 mph is actually 59.4 mph on 235/45R21, and revolutions per mile change from 681 to 688.

235/45R21 mounts on a 21-inch wheel, a plus-2 fitment from the 19-inch wheel of 245/55R19.

Size pages

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