215/55R16 vs 275/35R18

275/35R18 is 0.27 in (6.8 mm) taller than 215/55R16, a +1.06% diameter difference. With the speedometer set for 215/55R16, an indicated 60 mph is 60.6 mph on 275/35R18.

Is this a safe swap?

Diameter difference +1.06%: within the ±3% guideline

By overall diameter alone, 275/35R18 falls inside the ±3% range commonly used as a guideline when replacing 215/55R16. 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.

215/55R16 vs 275/35R18 differences
Measurement	215/55R16	275/35R18	Difference	% diff
Overall diameter	25.31 in (642.9 mm)	25.58 in (649.7 mm)	+0.27 in (+6.8 mm)	+1.06%
Sidewall height	4.66 in (118.3 mm)	3.79 in (96.3 mm)	−0.87 in (−22.0 mm)	−18.60%
Section width	8.46 in (215.0 mm)	10.83 in (275.0 mm)	+2.36 in (+60.0 mm)	+27.91%
Circumference	79.52 in (2,019.7 mm)	80.36 in (2,041.1 mm)	+0.84 in (+21.4 mm)	+1.06%
Revolutions per mile	797	788	−8	−1.05%

True speed with the speedometer calibrated for 215/55R16
Indicated	Actual on 215/55R16	Actual on 275/35R18	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.8 mph	+0.8 mph

Ride-height change: 275/35R18 raises the vehicle by 0.13 in (3.4 mm) at the axle (half the +6.8 mm diameter difference).

275/35R18 is 0.27 in taller than 215/55R16 and 60 mm wider, a 1.06% difference in overall diameter.

With the speedometer calibrated for 215/55R16, an indicated 60 mph is actually 60.6 mph on 275/35R18, and revolutions per mile change from 797 to 788.

275/35R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 215/55R16.

Size pages

Other comparisons with 215/55R16

Other comparisons with 275/35R18

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