215/50R18 vs 245/40R19

245/40R19 is 0.25 in (6.4 mm) taller than 215/50R18, a +0.95% diameter difference. With the speedometer set for 215/50R18, an indicated 60 mph is 60.6 mph on 245/40R19.

Is this a safe swap?

Diameter difference +0.95%: under 1%

By overall diameter alone, 245/40R19 is a near match for 215/50R18; 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.

215/50R18 vs 245/40R19 differences
Measurement	215/50R18	245/40R19	Difference	% diff
Overall diameter	26.46 in (672.2 mm)	26.72 in (678.6 mm)	+0.25 in (+6.4 mm)	+0.95%
Sidewall height	4.23 in (107.5 mm)	3.86 in (98.0 mm)	−0.37 in (−9.5 mm)	−8.84%
Section width	8.46 in (215.0 mm)	9.65 in (245.0 mm)	+1.18 in (+30.0 mm)	+13.95%
Circumference	83.14 in (2,111.8 mm)	83.93 in (2,131.9 mm)	+0.79 in (+20.1 mm)	+0.95%
Revolutions per mile	762	755	−7	−0.94%

True speed with the speedometer calibrated for 215/50R18
Indicated	Actual on 215/50R18	Actual on 245/40R19	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: 245/40R19 raises the vehicle by 0.13 in (3.2 mm) at the axle (half the +6.4 mm diameter difference).

245/40R19 is 0.25 in taller than 215/50R18 and 30 mm wider, a 0.95% difference in overall diameter.

With the speedometer calibrated for 215/50R18, an indicated 60 mph is actually 60.6 mph on 245/40R19, and revolutions per mile change from 762 to 755.

245/40R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 215/50R18.

Size pages

Other comparisons with 215/50R18

Other comparisons with 245/40R19

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