245/45R18 vs 265/45R18

265/45R18 is 0.71 in (18.0 mm) taller than 245/45R18, a +2.66% diameter difference. With the speedometer set for 245/45R18, an indicated 60 mph is 61.6 mph on 265/45R18.

Is this a safe swap?

Diameter difference +2.66%: within the ±3% guideline

By overall diameter alone, 265/45R18 falls inside the ±3% range commonly used as a guideline when replacing 245/45R18. 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.

245/45R18 vs 265/45R18 differences
Measurement	245/45R18	265/45R18	Difference	% diff
Overall diameter	26.68 in (677.7 mm)	27.39 in (695.7 mm)	+0.71 in (+18.0 mm)	+2.66%
Sidewall height	4.34 in (110.3 mm)	4.69 in (119.3 mm)	+0.35 in (+9.0 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	83.82 in (2,129.1 mm)	86.05 in (2,185.6 mm)	+2.23 in (+56.5 mm)	+2.66%
Revolutions per mile	756	736	−20	−2.59%

True speed with the speedometer calibrated for 245/45R18
Indicated	Actual on 245/45R18	Actual on 265/45R18	Difference
30 mph	30.0 mph	30.8 mph	+0.8 mph
60 mph	60.0 mph	61.6 mph	+1.6 mph
75 mph	75.0 mph	77.0 mph	+2.0 mph

Ride-height change: 265/45R18 raises the vehicle by 0.35 in (9.0 mm) at the axle (half the +18.0 mm diameter difference).

265/45R18 is 0.71 in taller than 245/45R18 and 20 mm wider, a 2.66% difference in overall diameter.

With the speedometer calibrated for 245/45R18, an indicated 60 mph is actually 61.6 mph on 265/45R18, and revolutions per mile change from 756 to 736.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 245/45R18

Other comparisons with 265/45R18

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