295/40R18 vs 265/45R18

265/45R18 is 0.10 in (2.5 mm) taller than 295/40R18, a +0.36% diameter difference. With the speedometer set for 295/40R18, an indicated 60 mph is 60.2 mph on 265/45R18.

Is this a safe swap?

Diameter difference +0.36%: under 1%

By overall diameter alone, 265/45R18 is a near match for 295/40R18; 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.

295/40R18 vs 265/45R18 differences
Measurement	295/40R18	265/45R18	Difference	% diff
Overall diameter	27.29 in (693.2 mm)	27.39 in (695.7 mm)	+0.10 in (+2.5 mm)	+0.36%
Sidewall height	4.65 in (118.0 mm)	4.69 in (119.3 mm)	+0.05 in (+1.3 mm)	+1.06%
Section width	11.61 in (295.0 mm)	10.43 in (265.0 mm)	−1.18 in (−30.0 mm)	−10.17%
Circumference	85.74 in (2,177.8 mm)	86.05 in (2,185.6 mm)	+0.31 in (+7.9 mm)	+0.36%
Revolutions per mile	739	736	−3	−0.36%

True speed with the speedometer calibrated for 295/40R18
Indicated	Actual on 295/40R18	Actual on 265/45R18	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	75.3 mph	+0.3 mph

Ride-height change: 265/45R18 raises the vehicle by 0.05 in (1.3 mm) at the axle (half the +2.5 mm diameter difference).

265/45R18 is 0.10 in taller than 295/40R18 and 30 mm narrower, a 0.36% difference in overall diameter.

With the speedometer calibrated for 295/40R18, an indicated 60 mph is actually 60.2 mph on 265/45R18, and revolutions per mile change from 739 to 736.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 295/40R18

Other comparisons with 265/45R18

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