235/35R18 vs 245/30R19

245/30R19 is 0.31 in (7.9 mm) taller than 235/35R18, a +1.27% diameter difference. With the speedometer set for 235/35R18, an indicated 60 mph is 60.8 mph on 245/30R19.

Is this a safe swap?

Diameter difference +1.27%: within the ±3% guideline

By overall diameter alone, 245/30R19 falls inside the ±3% range commonly used as a guideline when replacing 235/35R18. 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.

235/35R18 vs 245/30R19 differences
Measurement	235/35R18	245/30R19	Difference	% diff
Overall diameter	24.48 in (621.7 mm)	24.79 in (629.6 mm)	+0.31 in (+7.9 mm)	+1.27%
Sidewall height	3.24 in (82.3 mm)	2.89 in (73.5 mm)	−0.34 in (−8.7 mm)	−10.64%
Section width	9.25 in (235.0 mm)	9.65 in (245.0 mm)	+0.39 in (+10.0 mm)	+4.26%
Circumference	76.89 in (1,953.1 mm)	77.87 in (1,977.9 mm)	+0.98 in (+24.8 mm)	+1.27%
Revolutions per mile	824	814	−10	−1.25%

True speed with the speedometer calibrated for 235/35R18
Indicated	Actual on 235/35R18	Actual on 245/30R19	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.8 mph	+0.8 mph
75 mph	75.0 mph	76.0 mph	+1.0 mph

Ride-height change: 245/30R19 raises the vehicle by 0.16 in (3.9 mm) at the axle (half the +7.9 mm diameter difference).

245/30R19 is 0.31 in taller than 235/35R18 and 10 mm wider, a 1.27% difference in overall diameter.

With the speedometer calibrated for 235/35R18, an indicated 60 mph is actually 60.8 mph on 245/30R19, and revolutions per mile change from 824 to 814.

245/30R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 235/35R18.

Size pages

Other comparisons with 235/35R18

Other comparisons with 245/30R19

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