225/55R16 vs 215/45R18

215/45R18 is 0.13 in (3.2 mm) shorter than 225/55R16, a −0.49% diameter difference. With the speedometer set for 225/55R16, an indicated 60 mph is 59.7 mph on 215/45R18.

Is this a safe swap?

Diameter difference −0.49%: under 1%

By overall diameter alone, 215/45R18 is a near match for 225/55R16; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

225/55R16 vs 215/45R18 differences
Measurement	225/55R16	215/45R18	Difference	% diff
Overall diameter	25.74 in (653.9 mm)	25.62 in (650.7 mm)	−0.13 in (−3.2 mm)	−0.49%
Sidewall height	4.87 in (123.8 mm)	3.81 in (96.8 mm)	−1.06 in (−27.0 mm)	−21.82%
Section width	8.86 in (225.0 mm)	8.46 in (215.0 mm)	−0.39 in (−10.0 mm)	−4.44%
Circumference	80.88 in (2,054.3 mm)	80.48 in (2,044.2 mm)	−0.40 in (−10.1 mm)	−0.49%
Revolutions per mile	783	787	+4	+0.49%

True speed with the speedometer calibrated for 225/55R16
Indicated	Actual on 225/55R16	Actual on 215/45R18	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.7 mph	−0.3 mph
75 mph	75.0 mph	74.6 mph	−0.4 mph

Ride-height change: 215/45R18 lowers the vehicle by 0.06 in (1.6 mm) at the axle (half the −3.2 mm diameter difference).

215/45R18 is 0.13 in shorter than 225/55R16 and 10 mm narrower, a 0.49% difference in overall diameter.

With the speedometer calibrated for 225/55R16, an indicated 60 mph is actually 59.7 mph on 215/45R18, and revolutions per mile change from 783 to 787.

215/45R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 225/55R16.

Size pages

Other comparisons with 225/55R16

Other comparisons with 215/45R18

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.