225/35R19 vs 225/30R20

225/30R20 is 0.11 in (2.9 mm) taller than 225/35R19, a +0.45% diameter difference. With the speedometer set for 225/35R19, an indicated 60 mph is 60.3 mph on 225/30R20.

Is this a safe swap?

Diameter difference +0.45%: under 1%

By overall diameter alone, 225/30R20 is a near match for 225/35R19; 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.

225/35R19 vs 225/30R20 differences
Measurement	225/35R19	225/30R20	Difference	% diff
Overall diameter	25.20 in (640.1 mm)	25.31 in (643.0 mm)	+0.11 in (+2.9 mm)	+0.45%
Sidewall height	3.10 in (78.8 mm)	2.66 in (67.5 mm)	−0.44 in (−11.2 mm)	−14.29%
Section width	8.86 in (225.0 mm)	8.86 in (225.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	79.17 in (2,010.9 mm)	79.53 in (2,020.0 mm)	+0.36 in (+9.1 mm)	+0.45%
Revolutions per mile	800	797	−4	−0.45%

True speed with the speedometer calibrated for 225/35R19
Indicated	Actual on 225/35R19	Actual on 225/30R20	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	75.3 mph	+0.3 mph

Ride-height change: 225/30R20 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +2.9 mm diameter difference).

225/30R20 is 0.11 in taller than 225/35R19 and the same width, a 0.45% difference in overall diameter.

With the speedometer calibrated for 225/35R19, an indicated 60 mph is actually 60.3 mph on 225/30R20, and revolutions per mile change from 800 to 797.

225/30R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 225/35R19.

Size pages

Other comparisons with 225/35R19

Other comparisons with 225/30R20

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