TireSizesFinder

225/45R19 vs 225/40R20

225/40R20 is 0.11 in (2.9 mm) taller than 225/45R19, a +0.42% diameter difference. With the speedometer set for 225/45R19, an indicated 60 mph is 60.3 mph on 225/40R20.

Is this a safe swap?

Diameter difference +0.42%: under 1%

By overall diameter alone, 225/40R20 is a near match for 225/45R19; 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: 225/45R19 (26.97 in) vs 225/40R20 (27.09 in)225/45R1926.97 in × 8.86 in225/40R2027.09 in × 8.86 in
Side profile and tread width, drawn to the same scale.
225/45R19 vs 225/40R20 differences
Measurement225/45R19225/40R20Difference% diff
Overall diameter26.97 in (685.1 mm)27.09 in (688.0 mm)+0.11 in (+2.9 mm)+0.42%
Sidewall height3.99 in (101.3 mm)3.54 in (90.0 mm)−0.44 in (−11.2 mm)−11.11%
Section width8.86 in (225.0 mm)8.86 in (225.0 mm)0.00 in (0.0 mm)0.00%
Circumference84.74 in (2,152.3 mm)85.10 in (2,161.4 mm)+0.36 in (+9.1 mm)+0.42%
Revolutions per mile748745−3−0.42%
True speed with the speedometer calibrated for 225/45R19
IndicatedActual on 225/45R19Actual on 225/40R20Difference
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: 225/40R20 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +2.9 mm diameter difference).

225/40R20 is 0.11 in taller than 225/45R19 and the same width, a 0.42% difference in overall diameter.

With the speedometer calibrated for 225/45R19, an indicated 60 mph is actually 60.3 mph on 225/40R20, and revolutions per mile change from 748 to 745.

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

Size pages

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