295/35R18 vs 265/30R20

265/30R20 is 0.13 in (3.3 mm) taller than 295/35R18, a +0.50% diameter difference. With the speedometer set for 295/35R18, an indicated 60 mph is 60.3 mph on 265/30R20.

Is this a safe swap?

Diameter difference +0.50%: under 1%

By overall diameter alone, 265/30R20 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 265/30R20 differences
Measurement	295/35R18	265/30R20	Difference	% diff
Overall diameter	26.13 in (663.7 mm)	26.26 in (667.0 mm)	+0.13 in (+3.3 mm)	+0.50%
Sidewall height	4.06 in (103.3 mm)	3.13 in (79.5 mm)	−0.94 in (−23.7 mm)	−23.00%
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)	82.50 in (2,095.4 mm)	+0.41 in (+10.4 mm)	+0.50%
Revolutions per mile	772	768	−4	−0.49%

True speed with the speedometer calibrated for 295/35R18
Indicated	Actual on 295/35R18	Actual on 265/30R20	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.3 mph	+0.3 mph
75 mph	75.0 mph	75.4 mph	+0.4 mph

Ride-height change: 265/30R20 raises the vehicle by 0.06 in (1.6 mm) at the axle (half the +3.3 mm diameter difference).

265/30R20 is 0.13 in taller than 295/35R18 and 30 mm narrower, a 0.50% difference in overall diameter.

With the speedometer calibrated for 295/35R18, an indicated 60 mph is actually 60.3 mph on 265/30R20, and revolutions per mile change from 772 to 768.

265/30R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 295/35R18.

Size pages

Other comparisons with 295/35R18

Other comparisons with 265/30R20

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