255/85R16 vs 265/70R18

265/70R18 is 0.46 in (11.7 mm) shorter than 255/85R16, a −1.39% diameter difference. With the speedometer set for 255/85R16, an indicated 60 mph is 59.2 mph on 265/70R18.

Is this a safe swap?

Diameter difference −1.39%: within the ±3% guideline

By overall diameter alone, 265/70R18 falls inside the ±3% range commonly used as a guideline when replacing 255/85R16. 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.

255/85R16 vs 265/70R18 differences
Measurement	255/85R16	265/70R18	Difference	% diff
Overall diameter	33.07 in (839.9 mm)	32.61 in (828.2 mm)	−0.46 in (−11.7 mm)	−1.39%
Sidewall height	8.53 in (216.8 mm)	7.30 in (185.5 mm)	−1.23 in (−31.2 mm)	−14.42%
Section width	10.04 in (255.0 mm)	10.43 in (265.0 mm)	+0.39 in (+10.0 mm)	+3.92%
Circumference	103.88 in (2,638.6 mm)	102.44 in (2,601.9 mm)	−1.45 in (−36.8 mm)	−1.39%
Revolutions per mile	610	619	+9	+1.41%

True speed with the speedometer calibrated for 255/85R16
Indicated	Actual on 255/85R16	Actual on 265/70R18	Difference
30 mph	30.0 mph	29.6 mph	−0.4 mph
60 mph	60.0 mph	59.2 mph	−0.8 mph
75 mph	75.0 mph	74.0 mph	−1.0 mph

Ride-height change: 265/70R18 lowers the vehicle by 0.23 in (5.8 mm) at the axle (half the −11.7 mm diameter difference).

265/70R18 is 0.46 in shorter than 255/85R16 and 10 mm wider, a 1.39% difference in overall diameter.

With the speedometer calibrated for 255/85R16, an indicated 60 mph is actually 59.2 mph on 265/70R18, and revolutions per mile change from 610 to 619.

265/70R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 255/85R16.

Size pages

Other comparisons with 255/85R16

Other comparisons with 265/70R18

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