255/55R18 vs 275/45R19

275/45R19 is 0.30 in (7.6 mm) shorter than 255/55R18, a −1.03% diameter difference. With the speedometer set for 255/55R18, an indicated 60 mph is 59.4 mph on 275/45R19.

Is this a safe swap?

Diameter difference −1.03%: within the ±3% guideline

By overall diameter alone, 275/45R19 falls inside the ±3% range commonly used as a guideline when replacing 255/55R18. 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.

255/55R18 vs 275/45R19 differences
Measurement	255/55R18	275/45R19	Difference	% diff
Overall diameter	29.04 in (737.7 mm)	28.74 in (730.1 mm)	−0.30 in (−7.6 mm)	−1.03%
Sidewall height	5.52 in (140.3 mm)	4.87 in (123.8 mm)	−0.65 in (−16.5 mm)	−11.76%
Section width	10.04 in (255.0 mm)	10.83 in (275.0 mm)	+0.79 in (+20.0 mm)	+7.84%
Circumference	91.24 in (2,317.6 mm)	90.30 in (2,293.7 mm)	−0.94 in (−23.9 mm)	−1.03%
Revolutions per mile	694	702	+7	+1.04%

True speed with the speedometer calibrated for 255/55R18
Indicated	Actual on 255/55R18	Actual on 275/45R19	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.4 mph	−0.6 mph
75 mph	75.0 mph	74.2 mph	−0.8 mph

Ride-height change: 275/45R19 lowers the vehicle by 0.15 in (3.8 mm) at the axle (half the −7.6 mm diameter difference).

275/45R19 is 0.30 in shorter than 255/55R18 and 20 mm wider, a 1.03% difference in overall diameter.

With the speedometer calibrated for 255/55R18, an indicated 60 mph is actually 59.4 mph on 275/45R19, and revolutions per mile change from 694 to 702.

275/45R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 255/55R18.

Size pages

Other comparisons with 255/55R18

Other comparisons with 275/45R19

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