TireSizesFinder

225/55R17 vs 225/50R18

225/50R18 is 0.11 in (2.9 mm) taller than 225/55R17, a +0.43% diameter difference. With the speedometer set for 225/55R17, an indicated 60 mph is 60.3 mph on 225/50R18.

Is this a safe swap?

Diameter difference +0.43%: under 1%

By overall diameter alone, 225/50R18 is a near match for 225/55R17; 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: 225/55R17 (26.74 in) vs 225/50R18 (26.86 in)225/55R1726.74 in × 8.86 in225/50R1826.86 in × 8.86 in
Side profile and tread width, drawn to the same scale.
225/55R17 vs 225/50R18 differences
Measurement225/55R17225/50R18Difference% diff
Overall diameter26.74 in (679.3 mm)26.86 in (682.2 mm)+0.11 in (+2.9 mm)+0.43%
Sidewall height4.87 in (123.8 mm)4.43 in (112.5 mm)−0.44 in (−11.2 mm)−9.09%
Section width8.86 in (225.0 mm)8.86 in (225.0 mm)0.00 in (0.0 mm)0.00%
Circumference84.02 in (2,134.1 mm)84.38 in (2,143.2 mm)+0.36 in (+9.1 mm)+0.43%
Revolutions per mile754751−3−0.43%
True speed with the speedometer calibrated for 225/55R17
IndicatedActual on 225/55R17Actual on 225/50R18Difference
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: 225/50R18 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +2.9 mm diameter difference).

225/50R18 is 0.11 in taller than 225/55R17 and the same width, a 0.43% difference in overall diameter.

With the speedometer calibrated for 225/55R17, an indicated 60 mph is actually 60.3 mph on 225/50R18, and revolutions per mile change from 754 to 751.

225/50R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 225/55R17.

Size pages

Other comparisons with 225/55R17

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