285/35R18 vs 285/30R19

285/30R19 is 0.12 in (3.1 mm) shorter than 285/35R18, a −0.47% diameter difference. With the speedometer set for 285/35R18, an indicated 60 mph is 59.7 mph on 285/30R19.

Is this a safe swap?

Diameter difference −0.47%: under 1%

By overall diameter alone, 285/30R19 is a near match for 285/35R18; 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.

285/35R18 vs 285/30R19 differences
Measurement	285/35R18	285/30R19	Difference	% diff
Overall diameter	25.85 in (656.7 mm)	25.73 in (653.6 mm)	−0.12 in (−3.1 mm)	−0.47%
Sidewall height	3.93 in (99.8 mm)	3.37 in (85.5 mm)	−0.56 in (−14.2 mm)	−14.29%
Section width	11.22 in (285.0 mm)	11.22 in (285.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	81.22 in (2,063.1 mm)	80.84 in (2,053.3 mm)	−0.38 in (−9.7 mm)	−0.47%
Revolutions per mile	780	784	+4	+0.47%

True speed with the speedometer calibrated for 285/35R18
Indicated	Actual on 285/35R18	Actual on 285/30R19	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.7 mph	−0.3 mph
75 mph	75.0 mph	74.6 mph	−0.4 mph

Ride-height change: 285/30R19 lowers the vehicle by 0.06 in (1.6 mm) at the axle (half the −3.1 mm diameter difference).

285/30R19 is 0.12 in shorter than 285/35R18 and the same width, a 0.47% difference in overall diameter.

With the speedometer calibrated for 285/35R18, an indicated 60 mph is actually 59.7 mph on 285/30R19, and revolutions per mile change from 780 to 784.

285/30R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 285/35R18.

Size pages

Other comparisons with 285/35R18

Other comparisons with 285/30R19

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