235/45R19 vs 255/45R19

255/45R19 is 0.71 in (18.0 mm) taller than 235/45R19, a +2.59% diameter difference. With the speedometer set for 235/45R19, an indicated 60 mph is 61.6 mph on 255/45R19.

Is this a safe swap?

Diameter difference +2.59%: within the ±3% guideline

By overall diameter alone, 255/45R19 falls inside the ±3% range commonly used as a guideline when replacing 235/45R19. 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.

235/45R19 vs 255/45R19 differences
Measurement	235/45R19	255/45R19	Difference	% diff
Overall diameter	27.33 in (694.1 mm)	28.04 in (712.1 mm)	+0.71 in (+18.0 mm)	+2.59%
Sidewall height	4.16 in (105.8 mm)	4.52 in (114.8 mm)	+0.35 in (+9.0 mm)	+8.51%
Section width	9.25 in (235.0 mm)	10.04 in (255.0 mm)	+0.79 in (+20.0 mm)	+8.51%
Circumference	85.85 in (2,180.6 mm)	88.08 in (2,237.1 mm)	+2.23 in (+56.5 mm)	+2.59%
Revolutions per mile	738	719	−19	−2.53%

True speed with the speedometer calibrated for 235/45R19
Indicated	Actual on 235/45R19	Actual on 255/45R19	Difference
30 mph	30.0 mph	30.8 mph	+0.8 mph
60 mph	60.0 mph	61.6 mph	+1.6 mph
75 mph	75.0 mph	76.9 mph	+1.9 mph

Ride-height change: 255/45R19 raises the vehicle by 0.35 in (9.0 mm) at the axle (half the +18.0 mm diameter difference).

255/45R19 is 0.71 in taller than 235/45R19 and 20 mm wider, a 2.59% difference in overall diameter.

With the speedometer calibrated for 235/45R19, an indicated 60 mph is actually 61.6 mph on 255/45R19, and revolutions per mile change from 738 to 719.

Both sizes mount on 19-inch wheels.

Size pages

Other comparisons with 235/45R19

Other comparisons with 255/45R19

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