TireSizesFinder

225/50R18 vs 245/40R19

245/40R19 is 0.14 in (3.6 mm) shorter than 225/50R18, a −0.53% diameter difference. With the speedometer set for 225/50R18, an indicated 60 mph is 59.7 mph on 245/40R19.

Is this a safe swap?

Diameter difference −0.53%: under 1%

By overall diameter alone, 245/40R19 is a near match for 225/50R18; 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: 225/50R18 (26.86 in) vs 245/40R19 (26.72 in)225/50R1826.86 in × 8.86 in245/40R1926.72 in × 9.65 in
Side profile and tread width, drawn to the same scale.
225/50R18 vs 245/40R19 differences
Measurement225/50R18245/40R19Difference% diff
Overall diameter26.86 in (682.2 mm)26.72 in (678.6 mm)−0.14 in (−3.6 mm)−0.53%
Sidewall height4.43 in (112.5 mm)3.86 in (98.0 mm)−0.57 in (−14.5 mm)−12.89%
Section width8.86 in (225.0 mm)9.65 in (245.0 mm)+0.79 in (+20.0 mm)+8.89%
Circumference84.38 in (2,143.2 mm)83.93 in (2,131.9 mm)−0.45 in (−11.3 mm)−0.53%
Revolutions per mile751755+4+0.53%
True speed with the speedometer calibrated for 225/50R18
IndicatedActual on 225/50R18Actual on 245/40R19Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.7 mph−0.3 mph
75 mph75.0 mph74.6 mph−0.4 mph

Ride-height change: 245/40R19 lowers the vehicle by 0.07 in (1.8 mm) at the axle (half the −3.6 mm diameter difference).

245/40R19 is 0.14 in shorter than 225/50R18 and 20 mm wider, a 0.53% difference in overall diameter.

With the speedometer calibrated for 225/50R18, an indicated 60 mph is actually 59.7 mph on 245/40R19, and revolutions per mile change from 751 to 755.

245/40R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 225/50R18.

Size pages

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