245/35R18 vs 245/30R19

245/30R19 is 0.04 in (0.9 mm) taller than 245/35R18, a +0.14% diameter difference. With the speedometer set for 245/35R18, an indicated 60 mph is 60.1 mph on 245/30R19.

Is this a safe swap?

Diameter difference +0.14%: under 1%

By overall diameter alone, 245/30R19 is a near match for 245/35R18; 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.

245/35R18 vs 245/30R19 differences
Measurement	245/35R18	245/30R19	Difference	% diff
Overall diameter	24.75 in (628.7 mm)	24.79 in (629.6 mm)	+0.04 in (+0.9 mm)	+0.14%
Sidewall height	3.38 in (85.8 mm)	2.89 in (73.5 mm)	−0.48 in (−12.2 mm)	−14.29%
Section width	9.65 in (245.0 mm)	9.65 in (245.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	77.76 in (1,975.1 mm)	77.87 in (1,977.9 mm)	+0.11 in (+2.8 mm)	+0.14%
Revolutions per mile	815	814	−1	−0.14%

True speed with the speedometer calibrated for 245/35R18
Indicated	Actual on 245/35R18	Actual on 245/30R19	Difference
30 mph	30.0 mph	30.0 mph	0.0 mph
60 mph	60.0 mph	60.1 mph	+0.1 mph
75 mph	75.0 mph	75.1 mph	+0.1 mph

Ride-height change: 245/30R19 raises the vehicle by 0.02 in (0.4 mm) at the axle (half the +0.9 mm diameter difference).

245/30R19 is 0.04 in taller than 245/35R18 and the same width, a 0.14% difference in overall diameter.

With the speedometer calibrated for 245/35R18, an indicated 60 mph is actually 60.1 mph on 245/30R19, and revolutions per mile change from 815 to 814.

245/30R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 245/35R18.

Size pages

Other comparisons with 245/35R18

Other comparisons with 245/30R19

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