215/55R16 vs 265/35R18

265/35R18 is 0.01 in (0.2 mm) shorter than 215/55R16, a −0.03% diameter difference. With the speedometer set for 215/55R16, an indicated 60 mph is 60.0 mph on 265/35R18.

Is this a safe swap?

Diameter difference −0.03%: under 1%

By overall diameter alone, 265/35R18 is a near match for 215/55R16; 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.

215/55R16 vs 265/35R18 differences
Measurement	215/55R16	265/35R18	Difference	% diff
Overall diameter	25.31 in (642.9 mm)	25.30 in (642.7 mm)	−0.01 in (−0.2 mm)	−0.03%
Sidewall height	4.66 in (118.3 mm)	3.65 in (92.8 mm)	−1.00 in (−25.5 mm)	−21.56%
Section width	8.46 in (215.0 mm)	10.43 in (265.0 mm)	+1.97 in (+50.0 mm)	+23.26%
Circumference	79.52 in (2,019.7 mm)	79.49 in (2,019.1 mm)	−0.02 in (−0.6 mm)	−0.03%
Revolutions per mile	797	797	0	+0.03%

True speed with the speedometer calibrated for 215/55R16
Indicated	Actual on 215/55R16	Actual on 265/35R18
30 mph	30.0 mph	30.0 mph
60 mph	60.0 mph	60.0 mph
75 mph	75.0 mph	75.0 mph

Ride-height change: 265/35R18 lowers the vehicle by 0.00 in (0.1 mm) at the axle (half the −0.2 mm diameter difference).

265/35R18 is 0.01 in shorter than 215/55R16 and 50 mm wider, a 0.03% difference in overall diameter.

With the speedometer calibrated for 215/55R16, an indicated 60 mph is actually 60.0 mph on 265/35R18, and revolutions per mile change from 797 to 797.

265/35R18 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 265/35R18

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