TireSizesFinder

245/50R17 vs 215/50R18

215/50R18 is 0.18 in (4.6 mm) shorter than 245/50R17, a −0.68% diameter difference. With the speedometer set for 245/50R17, an indicated 60 mph is 59.6 mph on 215/50R18.

Is this a safe swap?

Diameter difference −0.68%: under 1%

By overall diameter alone, 215/50R18 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 215/50R18 (26.46 in)245/50R1726.65 in × 9.65 in215/50R1826.46 in × 8.46 in
Side profile and tread width, drawn to the same scale.
245/50R17 vs 215/50R18 differences
Measurement245/50R17215/50R18Difference% diff
Overall diameter26.65 in (676.8 mm)26.46 in (672.2 mm)−0.18 in (−4.6 mm)−0.68%
Sidewall height4.82 in (122.5 mm)4.23 in (107.5 mm)−0.59 in (−15.0 mm)−12.24%
Section width9.65 in (245.0 mm)8.46 in (215.0 mm)−1.18 in (−30.0 mm)−12.24%
Circumference83.71 in (2,126.2 mm)83.14 in (2,111.8 mm)−0.57 in (−14.5 mm)−0.68%
Revolutions per mile757762+5+0.68%
True speed with the speedometer calibrated for 245/50R17
IndicatedActual on 245/50R17Actual on 215/50R18Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.6 mph−0.4 mph
75 mph75.0 mph74.5 mph−0.5 mph

Ride-height change: 215/50R18 lowers the vehicle by 0.09 in (2.3 mm) at the axle (half the −4.6 mm diameter difference).

215/50R18 is 0.18 in shorter than 245/50R17 and 30 mm narrower, a 0.68% difference in overall diameter.

With the speedometer calibrated for 245/50R17, an indicated 60 mph is actually 59.6 mph on 215/50R18, and revolutions per mile change from 757 to 762.

215/50R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 245/50R17.

Size pages

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