295/30R20 vs 225/40R20

225/40R20 is 0.12 in (3.0 mm) taller than 295/30R20, a +0.44% diameter difference. With the speedometer set for 295/30R20, an indicated 60 mph is 60.3 mph on 225/40R20.

Is this a safe swap?

Diameter difference +0.44%: under 1%

By overall diameter alone, 225/40R20 is a near match for 295/30R20; 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.

295/30R20 vs 225/40R20 differences
Measurement	295/30R20	225/40R20	Difference	% diff
Overall diameter	26.97 in (685.0 mm)	27.09 in (688.0 mm)	+0.12 in (+3.0 mm)	+0.44%
Sidewall height	3.48 in (88.5 mm)	3.54 in (90.0 mm)	+0.06 in (+1.5 mm)	+1.69%
Section width	11.61 in (295.0 mm)	8.86 in (225.0 mm)	−2.76 in (−70.0 mm)	−23.73%
Circumference	84.72 in (2,152.0 mm)	85.10 in (2,161.4 mm)	+0.37 in (+9.4 mm)	+0.44%
Revolutions per mile	748	745	−3	−0.44%

True speed with the speedometer calibrated for 295/30R20
Indicated	Actual on 295/30R20	Actual on 225/40R20	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	75.3 mph	+0.3 mph

Ride-height change: 225/40R20 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +3.0 mm diameter difference).

225/40R20 is 0.12 in taller than 295/30R20 and 70 mm narrower, a 0.44% difference in overall diameter.

With the speedometer calibrated for 295/30R20, an indicated 60 mph is actually 60.3 mph on 225/40R20, and revolutions per mile change from 748 to 745.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 295/30R20

Other comparisons with 225/40R20

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