215/40R18 vs 245/30R19

245/30R19 is 0.02 in (0.4 mm) taller than 215/40R18, a +0.06% diameter difference. With the speedometer set for 215/40R18, an indicated 60 mph is 60.0 mph on 245/30R19.

Is this a safe swap?

Diameter difference +0.06%: under 1%

By overall diameter alone, 245/30R19 is a near match for 215/40R18; 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.

215/40R18 vs 245/30R19 differences
Measurement	215/40R18	245/30R19	Difference	% diff
Overall diameter	24.77 in (629.2 mm)	24.79 in (629.6 mm)	+0.02 in (+0.4 mm)	+0.06%
Sidewall height	3.39 in (86.0 mm)	2.89 in (73.5 mm)	−0.49 in (−12.5 mm)	−14.53%
Section width	8.46 in (215.0 mm)	9.65 in (245.0 mm)	+1.18 in (+30.0 mm)	+13.95%
Circumference	77.82 in (1,976.7 mm)	77.87 in (1,977.9 mm)	+0.05 in (+1.3 mm)	+0.06%
Revolutions per mile	814	814	−1	−0.06%

True speed with the speedometer calibrated for 215/40R18
Indicated	Actual on 215/40R18	Actual on 245/30R19
30 mph	30.0 mph	30.0 mph
60 mph	60.0 mph	60.0 mph
75 mph	75.0 mph	75.0 mph

Ride-height change: 245/30R19 raises the vehicle by 0.01 in (0.2 mm) at the axle (half the +0.4 mm diameter difference).

245/30R19 is 0.02 in taller than 215/40R18 and 30 mm wider, a 0.06% difference in overall diameter.

With the speedometer calibrated for 215/40R18, an indicated 60 mph is actually 60.0 mph on 245/30R19, and revolutions per mile change from 814 to 814.

245/30R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 215/40R18.

Size pages

Other comparisons with 215/40R18

Other comparisons with 245/30R19

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