225/60R17 vs 275/45R18

275/45R18 is 0.11 in (2.9 mm) taller than 225/60R17, a +0.41% diameter difference. With the speedometer set for 225/60R17, an indicated 60 mph is 60.2 mph on 275/45R18.

Is this a safe swap?

Diameter difference +0.41%: under 1%

By overall diameter alone, 275/45R18 is a near match for 225/60R17; 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.

225/60R17 vs 275/45R18 differences
Measurement	225/60R17	275/45R18	Difference	% diff
Overall diameter	27.63 in (701.8 mm)	27.74 in (704.7 mm)	+0.11 in (+2.9 mm)	+0.41%
Sidewall height	5.31 in (135.0 mm)	4.87 in (123.8 mm)	−0.44 in (−11.2 mm)	−8.33%
Section width	8.86 in (225.0 mm)	10.83 in (275.0 mm)	+1.97 in (+50.0 mm)	+22.22%
Circumference	86.80 in (2,204.8 mm)	87.16 in (2,213.9 mm)	+0.36 in (+9.1 mm)	+0.41%
Revolutions per mile	730	727	−3	−0.41%

True speed with the speedometer calibrated for 225/60R17
Indicated	Actual on 225/60R17	Actual on 275/45R18	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.3 mph	+0.3 mph

Ride-height change: 275/45R18 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +2.9 mm diameter difference).

275/45R18 is 0.11 in taller than 225/60R17 and 50 mm wider, a 0.41% difference in overall diameter.

With the speedometer calibrated for 225/60R17, an indicated 60 mph is actually 60.2 mph on 275/45R18, and revolutions per mile change from 730 to 727.

275/45R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 225/60R17.

Size pages

Other comparisons with 225/60R17

Other comparisons with 275/45R18

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