TireSizesFinder

245/50R17 vs 225/50R18

225/50R18 is 0.21 in (5.4 mm) taller than 245/50R17, a +0.80% diameter difference. With the speedometer set for 245/50R17, an indicated 60 mph is 60.5 mph on 225/50R18.

Is this a safe swap?

Diameter difference +0.80%: under 1%

By overall diameter alone, 225/50R18 is a near match for 245/50R17; 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: 245/50R17 (26.65 in) vs 225/50R18 (26.86 in)245/50R1726.65 in × 9.65 in225/50R1826.86 in × 8.86 in
Side profile and tread width, drawn to the same scale.
245/50R17 vs 225/50R18 differences
Measurement245/50R17225/50R18Difference% diff
Overall diameter26.65 in (676.8 mm)26.86 in (682.2 mm)+0.21 in (+5.4 mm)+0.80%
Sidewall height4.82 in (122.5 mm)4.43 in (112.5 mm)−0.39 in (−10.0 mm)−8.16%
Section width9.65 in (245.0 mm)8.86 in (225.0 mm)−0.79 in (−20.0 mm)−8.16%
Circumference83.71 in (2,126.2 mm)84.38 in (2,143.2 mm)+0.67 in (+17.0 mm)+0.80%
Revolutions per mile757751−6−0.79%
True speed with the speedometer calibrated for 245/50R17
IndicatedActual on 245/50R17Actual on 225/50R18Difference
30 mph30.0 mph30.2 mph+0.2 mph
60 mph60.0 mph60.5 mph+0.5 mph
75 mph75.0 mph75.6 mph+0.6 mph

Ride-height change: 225/50R18 raises the vehicle by 0.11 in (2.7 mm) at the axle (half the +5.4 mm diameter difference).

225/50R18 is 0.21 in taller than 245/50R17 and 20 mm narrower, a 0.80% difference in overall diameter.

With the speedometer calibrated for 245/50R17, an indicated 60 mph is actually 60.5 mph on 225/50R18, and revolutions per mile change from 757 to 751.

225/50R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 245/50R17.

Size pages

Other comparisons with 245/50R17

Other comparisons with 225/50R18

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