215/60R16 vs 265/40R18

265/40R18 is 0.19 in (4.8 mm) taller than 215/60R16, a +0.72% diameter difference. With the speedometer set for 215/60R16, an indicated 60 mph is 60.4 mph on 265/40R18.

Is this a safe swap?

Diameter difference +0.72%: under 1%

By overall diameter alone, 265/40R18 is a near match for 215/60R16; 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.

215/60R16 vs 265/40R18 differences
Measurement	215/60R16	265/40R18	Difference	% diff
Overall diameter	26.16 in (664.4 mm)	26.35 in (669.2 mm)	+0.19 in (+4.8 mm)	+0.72%
Sidewall height	5.08 in (129.0 mm)	4.17 in (106.0 mm)	−0.91 in (−23.0 mm)	−17.83%
Section width	8.46 in (215.0 mm)	10.43 in (265.0 mm)	+1.97 in (+50.0 mm)	+23.26%
Circumference	82.18 in (2,087.3 mm)	82.77 in (2,102.4 mm)	+0.59 in (+15.1 mm)	+0.72%
Revolutions per mile	771	765	−6	−0.72%

True speed with the speedometer calibrated for 215/60R16
Indicated	Actual on 215/60R16	Actual on 265/40R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.4 mph	+0.4 mph
75 mph	75.0 mph	75.5 mph	+0.5 mph

Ride-height change: 265/40R18 raises the vehicle by 0.09 in (2.4 mm) at the axle (half the +4.8 mm diameter difference).

265/40R18 is 0.19 in taller than 215/60R16 and 50 mm wider, a 0.72% difference in overall diameter.

With the speedometer calibrated for 215/60R16, an indicated 60 mph is actually 60.4 mph on 265/40R18, and revolutions per mile change from 771 to 765.

265/40R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 215/60R16.

Size pages

Other comparisons with 215/60R16

Other comparisons with 265/40R18

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