245/40R19 vs 225/45R19

225/45R19 is 0.26 in (6.5 mm) taller than 245/40R19, a +0.96% diameter difference. With the speedometer set for 245/40R19, an indicated 60 mph is 60.6 mph on 225/45R19.

Is this a safe swap?

Diameter difference +0.96%: under 1%

By overall diameter alone, 225/45R19 is a near match for 245/40R19; 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.

245/40R19 vs 225/45R19 differences
Measurement	245/40R19	225/45R19	Difference	% diff
Overall diameter	26.72 in (678.6 mm)	26.97 in (685.1 mm)	+0.26 in (+6.5 mm)	+0.96%
Sidewall height	3.86 in (98.0 mm)	3.99 in (101.3 mm)	+0.13 in (+3.3 mm)	+3.32%
Section width	9.65 in (245.0 mm)	8.86 in (225.0 mm)	−0.79 in (−20.0 mm)	−8.16%
Circumference	83.93 in (2,131.9 mm)	84.74 in (2,152.3 mm)	+0.80 in (+20.4 mm)	+0.96%
Revolutions per mile	755	748	−7	−0.95%

True speed with the speedometer calibrated for 245/40R19
Indicated	Actual on 245/40R19	Actual on 225/45R19	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.7 mph	+0.7 mph

Ride-height change: 225/45R19 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

225/45R19 is 0.26 in taller than 245/40R19 and 20 mm narrower, a 0.96% difference in overall diameter.

With the speedometer calibrated for 245/40R19, an indicated 60 mph is actually 60.6 mph on 225/45R19, and revolutions per mile change from 755 to 748.

Both sizes mount on 19-inch wheels.

Size pages

Other comparisons with 245/40R19

Other comparisons with 225/45R19

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