265/70R16 vs 255/65R18

255/65R18 is 0.44 in (11.3 mm) taller than 265/70R16, a +1.45% diameter difference. With the speedometer set for 265/70R16, an indicated 60 mph is 60.9 mph on 255/65R18.

Is this a safe swap?

Diameter difference +1.45%: within the ±3% guideline

By overall diameter alone, 255/65R18 falls inside the ±3% range commonly used as a guideline when replacing 265/70R16. 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.

265/70R16 vs 255/65R18 differences
Measurement	265/70R16	255/65R18	Difference	% diff
Overall diameter	30.61 in (777.4 mm)	31.05 in (788.7 mm)	+0.44 in (+11.3 mm)	+1.45%
Sidewall height	7.30 in (185.5 mm)	6.53 in (165.8 mm)	−0.78 in (−19.7 mm)	−10.65%
Section width	10.43 in (265.0 mm)	10.04 in (255.0 mm)	−0.39 in (−10.0 mm)	−3.77%
Circumference	96.15 in (2,442.3 mm)	97.55 in (2,477.8 mm)	+1.40 in (+35.5 mm)	+1.45%
Revolutions per mile	659	650	−9	−1.43%

True speed with the speedometer calibrated for 265/70R16
Indicated	Actual on 265/70R16	Actual on 255/65R18	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.9 mph	+0.9 mph
75 mph	75.0 mph	76.1 mph	+1.1 mph

Ride-height change: 255/65R18 raises the vehicle by 0.22 in (5.7 mm) at the axle (half the +11.3 mm diameter difference).

255/65R18 is 0.44 in taller than 265/70R16 and 10 mm narrower, a 1.45% difference in overall diameter.

With the speedometer calibrated for 265/70R16, an indicated 60 mph is actually 60.9 mph on 255/65R18, and revolutions per mile change from 659 to 650.

255/65R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 265/70R16.

Size pages

Other comparisons with 265/70R16

Other comparisons with 255/65R18

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