225/40R19 vs 305/30R19

305/30R19 is 0.12 in (3.0 mm) taller than 225/40R19, a +0.45% diameter difference. With the speedometer set for 225/40R19, an indicated 60 mph is 60.3 mph on 305/30R19.

Is this a safe swap?

Diameter difference +0.45%: under 1%

By overall diameter alone, 305/30R19 is a near match for 225/40R19; 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.

225/40R19 vs 305/30R19 differences
Measurement	225/40R19	305/30R19	Difference	% diff
Overall diameter	26.09 in (662.6 mm)	26.20 in (665.6 mm)	+0.12 in (+3.0 mm)	+0.45%
Sidewall height	3.54 in (90.0 mm)	3.60 in (91.5 mm)	+0.06 in (+1.5 mm)	+1.67%
Section width	8.86 in (225.0 mm)	12.01 in (305.0 mm)	+3.15 in (+80.0 mm)	+35.56%
Circumference	81.95 in (2,081.6 mm)	82.32 in (2,091.0 mm)	+0.37 in (+9.4 mm)	+0.45%
Revolutions per mile	773	770	−3	−0.45%

True speed with the speedometer calibrated for 225/40R19
Indicated	Actual on 225/40R19	Actual on 305/30R19	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: 305/30R19 raises the vehicle by 0.06 in (1.5 mm) at the axle (half the +3.0 mm diameter difference).

305/30R19 is 0.12 in taller than 225/40R19 and 80 mm wider, a 0.45% difference in overall diameter.

With the speedometer calibrated for 225/40R19, an indicated 60 mph is actually 60.3 mph on 305/30R19, and revolutions per mile change from 773 to 770.

Both sizes mount on 19-inch wheels.

Size pages

Other comparisons with 225/40R19

Other comparisons with 305/30R19

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