215/75R16 vs 245/55R18

245/55R18 is 0.09 in (2.2 mm) shorter than 215/75R16, a −0.30% diameter difference. With the speedometer set for 215/75R16, an indicated 60 mph is 59.8 mph on 245/55R18.

Is this a safe swap?

Diameter difference −0.30%: under 1%

By overall diameter alone, 245/55R18 is a near match for 215/75R16; 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.

215/75R16 vs 245/55R18 differences
Measurement	215/75R16	245/55R18	Difference	% diff
Overall diameter	28.70 in (728.9 mm)	28.61 in (726.7 mm)	−0.09 in (−2.2 mm)	−0.30%
Sidewall height	6.35 in (161.3 mm)	5.31 in (134.8 mm)	−1.04 in (−26.5 mm)	−16.43%
Section width	8.46 in (215.0 mm)	9.65 in (245.0 mm)	+1.18 in (+30.0 mm)	+13.95%
Circumference	90.15 in (2,289.9 mm)	89.88 in (2,283.0 mm)	−0.27 in (−6.9 mm)	−0.30%
Revolutions per mile	703	705	+2	+0.30%

True speed with the speedometer calibrated for 215/75R16
Indicated	Actual on 215/75R16	Actual on 245/55R18	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.8 mph	−0.2 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 245/55R18 lowers the vehicle by 0.04 in (1.1 mm) at the axle (half the −2.2 mm diameter difference).

245/55R18 is 0.09 in shorter than 215/75R16 and 30 mm wider, a 0.30% difference in overall diameter.

With the speedometer calibrated for 215/75R16, an indicated 60 mph is actually 59.8 mph on 245/55R18, and revolutions per mile change from 703 to 705.

245/55R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 215/75R16.

Size pages

Other comparisons with 215/75R16

Other comparisons with 245/55R18

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