245/75R17 vs 265/65R18

265/65R18 is 0.09 in (2.4 mm) taller than 245/75R17, a +0.30% diameter difference. With the speedometer set for 245/75R17, an indicated 60 mph is 60.2 mph on 265/65R18.

Is this a safe swap?

Diameter difference +0.30%: under 1%

By overall diameter alone, 265/65R18 is a near match for 245/75R17; the speedometer changes by less than 1%. 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.

245/75R17 vs 265/65R18 differences
Measurement	245/75R17	265/65R18	Difference	% diff
Overall diameter	31.47 in (799.3 mm)	31.56 in (801.7 mm)	+0.09 in (+2.4 mm)	+0.30%
Sidewall height	7.23 in (183.8 mm)	6.78 in (172.3 mm)	−0.45 in (−11.5 mm)	−6.26%
Section width	9.65 in (245.0 mm)	10.43 in (265.0 mm)	+0.79 in (+20.0 mm)	+8.16%
Circumference	98.86 in (2,511.1 mm)	99.16 in (2,518.6 mm)	+0.30 in (+7.5 mm)	+0.30%
Revolutions per mile	641	639	−2	−0.30%

True speed with the speedometer calibrated for 245/75R17
Indicated	Actual on 245/75R17	Actual on 265/65R18	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 265/65R18 raises the vehicle by 0.05 in (1.2 mm) at the axle (half the +2.4 mm diameter difference).

265/65R18 is 0.09 in taller than 245/75R17 and 20 mm wider, a 0.30% difference in overall diameter.

With the speedometer calibrated for 245/75R17, an indicated 60 mph is actually 60.2 mph on 265/65R18, and revolutions per mile change from 641 to 639.

265/65R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 245/75R17.

Size pages

Other comparisons with 245/75R17

Other comparisons with 265/65R18

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