TireSizesFinder

225/50R17 vs 215/45R18

215/45R18 is 0.24 in (6.1 mm) shorter than 225/50R17, a −0.93% diameter difference. With the speedometer set for 225/50R17, an indicated 60 mph is 59.4 mph on 215/45R18.

Is this a safe swap?

Diameter difference −0.93%: under 1%

By overall diameter alone, 215/45R18 is a near match for 225/50R17; 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: 225/50R17 (25.86 in) vs 215/45R18 (25.62 in)225/50R1725.86 in × 8.86 in215/45R1825.62 in × 8.46 in
Side profile and tread width, drawn to the same scale.
225/50R17 vs 215/45R18 differences
Measurement225/50R17215/45R18Difference% diff
Overall diameter25.86 in (656.8 mm)25.62 in (650.7 mm)−0.24 in (−6.1 mm)−0.93%
Sidewall height4.43 in (112.5 mm)3.81 in (96.8 mm)−0.62 in (−15.7 mm)−14.00%
Section width8.86 in (225.0 mm)8.46 in (215.0 mm)−0.39 in (−10.0 mm)−4.44%
Circumference81.24 in (2,063.4 mm)80.48 in (2,044.2 mm)−0.75 in (−19.2 mm)−0.93%
Revolutions per mile780787+7+0.94%
True speed with the speedometer calibrated for 225/50R17
IndicatedActual on 225/50R17Actual on 215/45R18Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.3 mph−0.7 mph

Ride-height change: 215/45R18 lowers the vehicle by 0.12 in (3.0 mm) at the axle (half the −6.1 mm diameter difference).

215/45R18 is 0.24 in shorter than 225/50R17 and 10 mm narrower, a 0.93% difference in overall diameter.

With the speedometer calibrated for 225/50R17, an indicated 60 mph is actually 59.4 mph on 215/45R18, and revolutions per mile change from 780 to 787.

215/45R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 225/50R17.

Size pages

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