245/40R17 vs 245/30R19

245/30R19 is 0.07 in (1.8 mm) taller than 245/40R17, a +0.29% diameter difference. With the speedometer set for 245/40R17, an indicated 60 mph is 60.2 mph on 245/30R19.

Is this a safe swap?

Diameter difference +0.29%: under 1%

By overall diameter alone, 245/30R19 is a near match for 245/40R17; 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.

245/40R17 vs 245/30R19 differences
Measurement	245/40R17	245/30R19	Difference	% diff
Overall diameter	24.72 in (627.8 mm)	24.79 in (629.6 mm)	+0.07 in (+1.8 mm)	+0.29%
Sidewall height	3.86 in (98.0 mm)	2.89 in (73.5 mm)	−0.96 in (−24.5 mm)	−25.00%
Section width	9.65 in (245.0 mm)	9.65 in (245.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	77.65 in (1,972.3 mm)	77.87 in (1,977.9 mm)	+0.22 in (+5.7 mm)	+0.29%
Revolutions per mile	816	814	−2	−0.29%

True speed with the speedometer calibrated for 245/40R17
Indicated	Actual on 245/40R17	Actual on 245/30R19	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 245/30R19 raises the vehicle by 0.04 in (0.9 mm) at the axle (half the +1.8 mm diameter difference).

245/30R19 is 0.07 in taller than 245/40R17 and the same width, a 0.29% difference in overall diameter.

With the speedometer calibrated for 245/40R17, an indicated 60 mph is actually 60.2 mph on 245/30R19, and revolutions per mile change from 816 to 814.

245/30R19 mounts on a 19-inch wheel, a plus-2 fitment from the 17-inch wheel of 245/40R17.

Size pages

Other comparisons with 245/40R17

Other comparisons with 245/30R19

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