255/50R18 vs 235/50R19

235/50R19 is 0.21 in (5.4 mm) taller than 255/50R18, a +0.76% diameter difference. With the speedometer set for 255/50R18, an indicated 60 mph is 60.5 mph on 235/50R19.

Is this a safe swap?

Diameter difference +0.76%: under 1%

By overall diameter alone, 235/50R19 is a near match for 255/50R18; 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.

255/50R18 vs 235/50R19 differences
Measurement	255/50R18	235/50R19	Difference	% diff
Overall diameter	28.04 in (712.2 mm)	28.25 in (717.6 mm)	+0.21 in (+5.4 mm)	+0.76%
Sidewall height	5.02 in (127.5 mm)	4.63 in (117.5 mm)	−0.39 in (−10.0 mm)	−7.84%
Section width	10.04 in (255.0 mm)	9.25 in (235.0 mm)	−0.79 in (−20.0 mm)	−7.84%
Circumference	88.09 in (2,237.4 mm)	88.76 in (2,254.4 mm)	+0.67 in (+17.0 mm)	+0.76%
Revolutions per mile	719	714	−5	−0.75%

True speed with the speedometer calibrated for 255/50R18
Indicated	Actual on 255/50R18	Actual on 235/50R19	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 235/50R19 raises the vehicle by 0.11 in (2.7 mm) at the axle (half the +5.4 mm diameter difference).

235/50R19 is 0.21 in taller than 255/50R18 and 20 mm narrower, a 0.76% difference in overall diameter.

With the speedometer calibrated for 255/50R18, an indicated 60 mph is actually 60.5 mph on 235/50R19, and revolutions per mile change from 719 to 714.

235/50R19 mounts on a 19-inch wheel, a plus-1 fitment from the 18-inch wheel of 255/50R18.

Size pages

Other comparisons with 255/50R18

Other comparisons with 235/50R19

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