245/35R18 vs 265/35R18

265/35R18 is 0.55 in (14.0 mm) taller than 245/35R18, a +2.23% diameter difference. With the speedometer set for 245/35R18, an indicated 60 mph is 61.3 mph on 265/35R18.

Is this a safe swap?

Diameter difference +2.23%: within the ±3% guideline

By overall diameter alone, 265/35R18 falls inside the ±3% range commonly used as a guideline when replacing 245/35R18. 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.

245/35R18 vs 265/35R18 differences
Measurement	245/35R18	265/35R18	Difference	% diff
Overall diameter	24.75 in (628.7 mm)	25.30 in (642.7 mm)	+0.55 in (+14.0 mm)	+2.23%
Sidewall height	3.38 in (85.8 mm)	3.65 in (92.8 mm)	+0.28 in (+7.0 mm)	+8.16%
Section width	9.65 in (245.0 mm)	10.43 in (265.0 mm)	+0.79 in (+20.0 mm)	+8.16%
Circumference	77.76 in (1,975.1 mm)	79.49 in (2,019.1 mm)	+1.73 in (+44.0 mm)	+2.23%
Revolutions per mile	815	797	−18	−2.18%

True speed with the speedometer calibrated for 245/35R18
Indicated	Actual on 245/35R18	Actual on 265/35R18	Difference
30 mph	30.0 mph	30.7 mph	+0.7 mph
60 mph	60.0 mph	61.3 mph	+1.3 mph
75 mph	75.0 mph	76.7 mph	+1.7 mph

Ride-height change: 265/35R18 raises the vehicle by 0.28 in (7.0 mm) at the axle (half the +14.0 mm diameter difference).

265/35R18 is 0.55 in taller than 245/35R18 and 20 mm wider, a 2.23% difference in overall diameter.

With the speedometer calibrated for 245/35R18, an indicated 60 mph is actually 61.3 mph on 265/35R18, and revolutions per mile change from 815 to 797.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 245/35R18

Other comparisons with 265/35R18

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