205/60R16 vs 275/35R18

275/35R18 is 0.11 in (2.7 mm) shorter than 205/60R16, a −0.41% diameter difference. With the speedometer set for 205/60R16, an indicated 60 mph is 59.8 mph on 275/35R18.

Is this a safe swap?

Diameter difference −0.41%: under 1%

By overall diameter alone, 275/35R18 is a near match for 205/60R16; 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.

205/60R16 vs 275/35R18 differences
Measurement	205/60R16	275/35R18	Difference	% diff
Overall diameter	25.69 in (652.4 mm)	25.58 in (649.7 mm)	−0.11 in (−2.7 mm)	−0.41%
Sidewall height	4.84 in (123.0 mm)	3.79 in (96.3 mm)	−1.05 in (−26.7 mm)	−21.75%
Section width	8.07 in (205.0 mm)	10.83 in (275.0 mm)	+2.76 in (+70.0 mm)	+34.15%
Circumference	80.69 in (2,049.6 mm)	80.36 in (2,041.1 mm)	−0.33 in (−8.5 mm)	−0.41%
Revolutions per mile	785	788	+3	+0.42%

True speed with the speedometer calibrated for 205/60R16
Indicated	Actual on 205/60R16	Actual on 275/35R18	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: 275/35R18 lowers the vehicle by 0.05 in (1.3 mm) at the axle (half the −2.7 mm diameter difference).

275/35R18 is 0.11 in shorter than 205/60R16 and 70 mm wider, a 0.41% difference in overall diameter.

With the speedometer calibrated for 205/60R16, an indicated 60 mph is actually 59.8 mph on 275/35R18, and revolutions per mile change from 785 to 788.

275/35R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 205/60R16.

Size pages

Other comparisons with 205/60R16

Other comparisons with 275/35R18

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