245/50R18 vs 265/50R18

265/50R18 is 0.79 in (20.0 mm) taller than 245/50R18, a +2.85% diameter difference. With the speedometer set for 245/50R18, an indicated 60 mph is 61.7 mph on 265/50R18.

Is this a safe swap?

Diameter difference +2.85%: within the ±3% guideline

By overall diameter alone, 265/50R18 falls inside the ±3% range commonly used as a guideline when replacing 245/50R18. 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.

245/50R18 vs 265/50R18 differences
Measurement	245/50R18	265/50R18	Difference	% diff
Overall diameter	27.65 in (702.2 mm)	28.43 in (722.2 mm)	+0.79 in (+20.0 mm)	+2.85%
Sidewall height	4.82 in (122.5 mm)	5.22 in (132.5 mm)	+0.39 in (+10.0 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	86.85 in (2,206.0 mm)	89.33 in (2,268.9 mm)	+2.47 in (+62.8 mm)	+2.85%
Revolutions per mile	730	709	−20	−2.77%

True speed with the speedometer calibrated for 245/50R18
Indicated	Actual on 245/50R18	Actual on 265/50R18	Difference
30 mph	30.0 mph	30.9 mph	+0.9 mph
60 mph	60.0 mph	61.7 mph	+1.7 mph
75 mph	75.0 mph	77.1 mph	+2.1 mph

Ride-height change: 265/50R18 raises the vehicle by 0.39 in (10.0 mm) at the axle (half the +20.0 mm diameter difference).

265/50R18 is 0.79 in taller than 245/50R18 and 20 mm wider, a 2.85% difference in overall diameter.

With the speedometer calibrated for 245/50R18, an indicated 60 mph is actually 61.7 mph on 265/50R18, and revolutions per mile change from 730 to 709.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 245/50R18

Other comparisons with 265/50R18

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