285/45R18 vs 255/45R19

255/45R19 is 0.06 in (1.6 mm) shorter than 285/45R18, a −0.22% diameter difference. With the speedometer set for 285/45R18, an indicated 60 mph is 59.9 mph on 255/45R19.

Is this a safe swap?

Diameter difference −0.22%: under 1%

By overall diameter alone, 255/45R19 is a near match for 285/45R18; 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.

285/45R18 vs 255/45R19 differences
Measurement	285/45R18	255/45R19	Difference	% diff
Overall diameter	28.10 in (713.7 mm)	28.04 in (712.1 mm)	−0.06 in (−1.6 mm)	−0.22%
Sidewall height	5.05 in (128.3 mm)	4.52 in (114.8 mm)	−0.53 in (−13.5 mm)	−10.53%
Section width	11.22 in (285.0 mm)	10.04 in (255.0 mm)	−1.18 in (−30.0 mm)	−10.53%
Circumference	88.27 in (2,242.2 mm)	88.08 in (2,237.1 mm)	−0.20 in (−5.0 mm)	−0.22%
Revolutions per mile	718	719	+2	+0.22%

True speed with the speedometer calibrated for 285/45R18
Indicated	Actual on 285/45R18	Actual on 255/45R19	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.9 mph	−0.1 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 255/45R19 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.6 mm diameter difference).

255/45R19 is 0.06 in shorter than 285/45R18 and 30 mm narrower, a 0.22% difference in overall diameter.

With the speedometer calibrated for 285/45R18, an indicated 60 mph is actually 59.9 mph on 255/45R19, and revolutions per mile change from 718 to 719.

255/45R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 285/45R18.

Size pages

Other comparisons with 285/45R18

Other comparisons with 255/45R19

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