295/40R18 vs 265/35R20

265/35R20 is 0.01 in (0.3 mm) taller than 295/40R18, a +0.04% diameter difference. With the speedometer set for 295/40R18, an indicated 60 mph is 60.0 mph on 265/35R20.

Is this a safe swap?

Diameter difference +0.04%: under 1%

By overall diameter alone, 265/35R20 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 265/35R20 differences
Measurement	295/40R18	265/35R20	Difference	% diff
Overall diameter	27.29 in (693.2 mm)	27.30 in (693.5 mm)	+0.01 in (+0.3 mm)	+0.04%
Sidewall height	4.65 in (118.0 mm)	3.65 in (92.8 mm)	−0.99 in (−25.2 mm)	−21.40%
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)	85.78 in (2,178.7 mm)	+0.04 in (+0.9 mm)	+0.04%
Revolutions per mile	739	739	0	−0.04%

True speed with the speedometer calibrated for 295/40R18
Indicated	Actual on 295/40R18	Actual on 265/35R20
30 mph	30.0 mph	30.0 mph
60 mph	60.0 mph	60.0 mph
75 mph	75.0 mph	75.0 mph

Ride-height change: 265/35R20 raises the vehicle by 0.01 in (0.1 mm) at the axle (half the +0.3 mm diameter difference).

265/35R20 is 0.01 in taller than 295/40R18 and 30 mm narrower, a 0.04% difference in overall diameter.

With the speedometer calibrated for 295/40R18, an indicated 60 mph is actually 60.0 mph on 265/35R20, and revolutions per mile change from 739 to 739.

265/35R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 295/40R18.

Size pages

Other comparisons with 295/40R18

Other comparisons with 265/35R20

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