265/75R16 vs 255/70R18

255/70R18 is 0.41 in (10.3 mm) taller than 265/75R16, a +1.28% diameter difference. With the speedometer set for 265/75R16, an indicated 60 mph is 60.8 mph on 255/70R18.

Is this a safe swap?

Diameter difference +1.28%: within the ±3% guideline

By overall diameter alone, 255/70R18 falls inside the ±3% range commonly used as a guideline when replacing 265/75R16. 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.

265/75R16 vs 255/70R18 differences
Measurement	265/75R16	255/70R18	Difference	% diff
Overall diameter	31.65 in (803.9 mm)	32.06 in (814.2 mm)	+0.41 in (+10.3 mm)	+1.28%
Sidewall height	7.82 in (198.8 mm)	7.03 in (178.5 mm)	−0.80 in (−20.2 mm)	−10.19%
Section width	10.43 in (265.0 mm)	10.04 in (255.0 mm)	−0.39 in (−10.0 mm)	−3.77%
Circumference	99.43 in (2,525.5 mm)	100.70 in (2,557.9 mm)	+1.27 in (+32.4 mm)	+1.28%
Revolutions per mile	637	629	−8	−1.27%

True speed with the speedometer calibrated for 265/75R16
Indicated	Actual on 265/75R16	Actual on 255/70R18	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.8 mph	+0.8 mph
75 mph	75.0 mph	76.0 mph	+1.0 mph

Ride-height change: 255/70R18 raises the vehicle by 0.20 in (5.2 mm) at the axle (half the +10.3 mm diameter difference).

255/70R18 is 0.41 in taller than 265/75R16 and 10 mm narrower, a 1.28% difference in overall diameter.

With the speedometer calibrated for 265/75R16, an indicated 60 mph is actually 60.8 mph on 255/70R18, and revolutions per mile change from 637 to 629.

255/70R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 265/75R16.

Size pages

Other comparisons with 265/75R16

Other comparisons with 255/70R18

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