255/65R18 vs 265/65R18

265/65R18 is 0.51 in (13.0 mm) taller than 255/65R18, a +1.65% diameter difference. With the speedometer set for 255/65R18, an indicated 60 mph is 61.0 mph on 265/65R18.

Is this a safe swap?

Diameter difference +1.65%: within the ±3% guideline

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

255/65R18 vs 265/65R18 differences
Measurement	255/65R18	265/65R18	Difference	% diff
Overall diameter	31.05 in (788.7 mm)	31.56 in (801.7 mm)	+0.51 in (+13.0 mm)	+1.65%
Sidewall height	6.53 in (165.8 mm)	6.78 in (172.3 mm)	+0.26 in (+6.5 mm)	+3.92%
Section width	10.04 in (255.0 mm)	10.43 in (265.0 mm)	+0.39 in (+10.0 mm)	+3.92%
Circumference	97.55 in (2,477.8 mm)	99.16 in (2,518.6 mm)	+1.61 in (+40.8 mm)	+1.65%
Revolutions per mile	650	639	−11	−1.62%

True speed with the speedometer calibrated for 255/65R18
Indicated	Actual on 255/65R18	Actual on 265/65R18	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	61.0 mph	+1.0 mph
75 mph	75.0 mph	76.2 mph	+1.2 mph

Ride-height change: 265/65R18 raises the vehicle by 0.26 in (6.5 mm) at the axle (half the +13.0 mm diameter difference).

265/65R18 is 0.51 in taller than 255/65R18 and 10 mm wider, a 1.65% difference in overall diameter.

With the speedometer calibrated for 255/65R18, an indicated 60 mph is actually 61.0 mph on 265/65R18, and revolutions per mile change from 650 to 639.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 255/65R18

Other comparisons with 265/65R18

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