225/65R16 vs 275/45R18

275/45R18 is 0.23 in (5.8 mm) taller than 225/65R16, a +0.83% diameter difference. With the speedometer set for 225/65R16, an indicated 60 mph is 60.5 mph on 275/45R18.

Is this a safe swap?

Diameter difference +0.83%: under 1%

By overall diameter alone, 275/45R18 is a near match for 225/65R16; 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.

225/65R16 vs 275/45R18 differences
Measurement	225/65R16	275/45R18	Difference	% diff
Overall diameter	27.52 in (698.9 mm)	27.74 in (704.7 mm)	+0.23 in (+5.8 mm)	+0.83%
Sidewall height	5.76 in (146.3 mm)	4.87 in (123.8 mm)	−0.89 in (−22.5 mm)	−15.38%
Section width	8.86 in (225.0 mm)	10.83 in (275.0 mm)	+1.97 in (+50.0 mm)	+22.22%
Circumference	86.44 in (2,195.7 mm)	87.16 in (2,213.9 mm)	+0.72 in (+18.2 mm)	+0.83%
Revolutions per mile	733	727	−6	−0.82%

True speed with the speedometer calibrated for 225/65R16
Indicated	Actual on 225/65R16	Actual on 275/45R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 275/45R18 raises the vehicle by 0.11 in (2.9 mm) at the axle (half the +5.8 mm diameter difference).

275/45R18 is 0.23 in taller than 225/65R16 and 50 mm wider, a 0.83% difference in overall diameter.

With the speedometer calibrated for 225/65R16, an indicated 60 mph is actually 60.5 mph on 275/45R18, and revolutions per mile change from 733 to 727.

275/45R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 225/65R16.

Size pages

Other comparisons with 225/65R16

Other comparisons with 275/45R18

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