225/55R18 vs 275/40R19

275/40R19 is 0.08 in (2.1 mm) shorter than 225/55R18, a −0.30% diameter difference. With the speedometer set for 225/55R18, an indicated 60 mph is 59.8 mph on 275/40R19.

Is this a safe swap?

Diameter difference −0.30%: under 1%

By overall diameter alone, 275/40R19 is a near match for 225/55R18; 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.

225/55R18 vs 275/40R19 differences
Measurement	225/55R18	275/40R19	Difference	% diff
Overall diameter	27.74 in (704.7 mm)	27.66 in (702.6 mm)	−0.08 in (−2.1 mm)	−0.30%
Sidewall height	4.87 in (123.8 mm)	4.33 in (110.0 mm)	−0.54 in (−13.7 mm)	−11.11%
Section width	8.86 in (225.0 mm)	10.83 in (275.0 mm)	+1.97 in (+50.0 mm)	+22.22%
Circumference	87.16 in (2,213.9 mm)	86.90 in (2,207.3 mm)	−0.26 in (−6.6 mm)	−0.30%
Revolutions per mile	727	729	+2	+0.30%

True speed with the speedometer calibrated for 225/55R18
Indicated	Actual on 225/55R18	Actual on 275/40R19	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.8 mph	−0.2 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 275/40R19 lowers the vehicle by 0.04 in (1.1 mm) at the axle (half the −2.1 mm diameter difference).

275/40R19 is 0.08 in shorter than 225/55R18 and 50 mm wider, a 0.30% difference in overall diameter.

With the speedometer calibrated for 225/55R18, an indicated 60 mph is actually 59.8 mph on 275/40R19, and revolutions per mile change from 727 to 729.

275/40R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 225/55R18.

Size pages

Other comparisons with 225/55R18

Other comparisons with 275/40R19

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