295/35R18 vs 265/40R18

265/40R18 is 0.22 in (5.5 mm) taller than 295/35R18, a +0.83% diameter difference. With the speedometer set for 295/35R18, an indicated 60 mph is 60.5 mph on 265/40R18.

Is this a safe swap?

Diameter difference +0.83%: under 1%

By overall diameter alone, 265/40R18 is a near match for 295/35R18; 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.

295/35R18 vs 265/40R18 differences
Measurement	295/35R18	265/40R18	Difference	% diff
Overall diameter	26.13 in (663.7 mm)	26.35 in (669.2 mm)	+0.22 in (+5.5 mm)	+0.83%
Sidewall height	4.06 in (103.3 mm)	4.17 in (106.0 mm)	+0.11 in (+2.8 mm)	+2.66%
Section width	11.61 in (295.0 mm)	10.43 in (265.0 mm)	−1.18 in (−30.0 mm)	−10.17%
Circumference	82.09 in (2,085.1 mm)	82.77 in (2,102.4 mm)	+0.68 in (+17.3 mm)	+0.83%
Revolutions per mile	772	765	−6	−0.82%

True speed with the speedometer calibrated for 295/35R18
Indicated	Actual on 295/35R18	Actual on 265/40R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 265/40R18 raises the vehicle by 0.11 in (2.8 mm) at the axle (half the +5.5 mm diameter difference).

265/40R18 is 0.22 in taller than 295/35R18 and 30 mm narrower, a 0.83% difference in overall diameter.

With the speedometer calibrated for 295/35R18, an indicated 60 mph is actually 60.5 mph on 265/40R18, and revolutions per mile change from 772 to 765.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 295/35R18

Other comparisons with 265/40R18

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