215/70R16 vs 275/45R18

275/45R18 is 0.11 in (2.7 mm) shorter than 215/70R16, a −0.38% diameter difference. With the speedometer set for 215/70R16, an indicated 60 mph is 59.8 mph on 275/45R18.

Is this a safe swap?

Diameter difference −0.38%: under 1%

By overall diameter alone, 275/45R18 is a near match for 215/70R16; 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.

215/70R16 vs 275/45R18 differences
Measurement	215/70R16	275/45R18	Difference	% diff
Overall diameter	27.85 in (707.4 mm)	27.74 in (704.7 mm)	−0.11 in (−2.7 mm)	−0.38%
Sidewall height	5.93 in (150.5 mm)	4.87 in (123.8 mm)	−1.05 in (−26.7 mm)	−17.77%
Section width	8.46 in (215.0 mm)	10.83 in (275.0 mm)	+2.36 in (+60.0 mm)	+27.91%
Circumference	87.49 in (2,222.4 mm)	87.16 in (2,213.9 mm)	−0.33 in (−8.5 mm)	−0.38%
Revolutions per mile	724	727	+3	+0.38%

True speed with the speedometer calibrated for 215/70R16
Indicated	Actual on 215/70R16	Actual on 275/45R18	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	74.7 mph	−0.3 mph

Ride-height change: 275/45R18 lowers the vehicle by 0.05 in (1.3 mm) at the axle (half the −2.7 mm diameter difference).

275/45R18 is 0.11 in shorter than 215/70R16 and 60 mm wider, a 0.38% difference in overall diameter.

With the speedometer calibrated for 215/70R16, an indicated 60 mph is actually 59.8 mph on 275/45R18, and revolutions per mile change from 724 to 727.

275/45R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 215/70R16.

Size pages

Other comparisons with 215/70R16

Other comparisons with 275/45R18

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