TireSizesFinder

235/45R19 vs 225/40R20

225/40R20 is 0.24 in (6.1 mm) shorter than 235/45R19, a −0.88% diameter difference. With the speedometer set for 235/45R19, an indicated 60 mph is 59.5 mph on 225/40R20.

Is this a safe swap?

Diameter difference −0.88%: under 1%

By overall diameter alone, 225/40R20 is a near match for 235/45R19; 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: 235/45R19 (27.33 in) vs 225/40R20 (27.09 in)235/45R1927.33 in × 9.25 in225/40R2027.09 in × 8.86 in
Side profile and tread width, drawn to the same scale.
235/45R19 vs 225/40R20 differences
Measurement235/45R19225/40R20Difference% diff
Overall diameter27.33 in (694.1 mm)27.09 in (688.0 mm)−0.24 in (−6.1 mm)−0.88%
Sidewall height4.16 in (105.8 mm)3.54 in (90.0 mm)−0.62 in (−15.7 mm)−14.89%
Section width9.25 in (235.0 mm)8.86 in (225.0 mm)−0.39 in (−10.0 mm)−4.26%
Circumference85.85 in (2,180.6 mm)85.10 in (2,161.4 mm)−0.75 in (−19.2 mm)−0.88%
Revolutions per mile738745+7+0.89%
True speed with the speedometer calibrated for 235/45R19
IndicatedActual on 235/45R19Actual on 225/40R20Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.5 mph−0.5 mph
75 mph75.0 mph74.3 mph−0.7 mph

Ride-height change: 225/40R20 lowers the vehicle by 0.12 in (3.0 mm) at the axle (half the −6.1 mm diameter difference).

225/40R20 is 0.24 in shorter than 235/45R19 and 10 mm narrower, a 0.88% difference in overall diameter.

With the speedometer calibrated for 235/45R19, an indicated 60 mph is actually 59.5 mph on 225/40R20, and revolutions per mile change from 738 to 745.

225/40R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 235/45R19.

Size pages

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