225/55R16 vs 275/35R18

275/35R18 is 0.17 in (4.2 mm) shorter than 225/55R16, a −0.64% diameter difference. With the speedometer set for 225/55R16, an indicated 60 mph is 59.6 mph on 275/35R18.

Is this a safe swap?

Diameter difference −0.64%: under 1%

By overall diameter alone, 275/35R18 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 275/35R18 differences
Measurement	225/55R16	275/35R18	Difference	% diff
Overall diameter	25.74 in (653.9 mm)	25.58 in (649.7 mm)	−0.17 in (−4.2 mm)	−0.64%
Sidewall height	4.87 in (123.8 mm)	3.79 in (96.3 mm)	−1.08 in (−27.5 mm)	−22.22%
Section width	8.86 in (225.0 mm)	10.83 in (275.0 mm)	+1.97 in (+50.0 mm)	+22.22%
Circumference	80.88 in (2,054.3 mm)	80.36 in (2,041.1 mm)	−0.52 in (−13.2 mm)	−0.64%
Revolutions per mile	783	788	+5	+0.65%

True speed with the speedometer calibrated for 225/55R16
Indicated	Actual on 225/55R16	Actual on 275/35R18	Difference
30 mph	30.0 mph	29.8 mph	−0.2 mph
60 mph	60.0 mph	59.6 mph	−0.4 mph
75 mph	75.0 mph	74.5 mph	−0.5 mph

Ride-height change: 275/35R18 lowers the vehicle by 0.08 in (2.1 mm) at the axle (half the −4.2 mm diameter difference).

275/35R18 is 0.17 in shorter than 225/55R16 and 50 mm wider, a 0.64% difference in overall diameter.

With the speedometer calibrated for 225/55R16, an indicated 60 mph is actually 59.6 mph on 275/35R18, and revolutions per mile change from 783 to 788.

275/35R18 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 275/35R18

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