285/35R19 vs 225/40R20

225/40R20 is 0.23 in (5.9 mm) taller than 285/35R19, a +0.86% diameter difference. With the speedometer set for 285/35R19, an indicated 60 mph is 60.5 mph on 225/40R20.

Is this a safe swap?

Diameter difference +0.86%: under 1%

By overall diameter alone, 225/40R20 is a near match for 285/35R19; 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.

285/35R19 vs 225/40R20 differences
Measurement	285/35R19	225/40R20	Difference	% diff
Overall diameter	26.85 in (682.1 mm)	27.09 in (688.0 mm)	+0.23 in (+5.9 mm)	+0.86%
Sidewall height	3.93 in (99.8 mm)	3.54 in (90.0 mm)	−0.38 in (−9.7 mm)	−9.77%
Section width	11.22 in (285.0 mm)	8.86 in (225.0 mm)	−2.36 in (−60.0 mm)	−21.05%
Circumference	84.37 in (2,142.9 mm)	85.10 in (2,161.4 mm)	+0.73 in (+18.5 mm)	+0.86%
Revolutions per mile	751	745	−6	−0.86%

True speed with the speedometer calibrated for 285/35R19
Indicated	Actual on 285/35R19	Actual on 225/40R20	Difference
30 mph	30.0 mph	30.3 mph	+0.3 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: 225/40R20 raises the vehicle by 0.12 in (3.0 mm) at the axle (half the +5.9 mm diameter difference).

225/40R20 is 0.23 in taller than 285/35R19 and 60 mm narrower, a 0.86% difference in overall diameter.

With the speedometer calibrated for 285/35R19, an indicated 60 mph is actually 60.5 mph on 225/40R20, and revolutions per mile change from 751 to 745.

225/40R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 285/35R19.

Size pages

Other comparisons with 285/35R19

Other comparisons with 225/40R20

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