255/40R19 vs 265/35R20

265/35R20 is 0.27 in (6.9 mm) taller than 255/40R19, a +1.00% diameter difference. With the speedometer set for 255/40R19, an indicated 60 mph is 60.6 mph on 265/35R20.

Is this a safe swap?

Diameter difference +1.00%: within the ±3% guideline

By overall diameter alone, 265/35R20 falls inside the ±3% range commonly used as a guideline when replacing 255/40R19. 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.

255/40R19 vs 265/35R20 differences
Measurement	255/40R19	265/35R20	Difference	% diff
Overall diameter	27.03 in (686.6 mm)	27.30 in (693.5 mm)	+0.27 in (+6.9 mm)	+1.00%
Sidewall height	4.02 in (102.0 mm)	3.65 in (92.8 mm)	−0.36 in (−9.2 mm)	−9.07%
Section width	10.04 in (255.0 mm)	10.43 in (265.0 mm)	+0.39 in (+10.0 mm)	+3.92%
Circumference	84.92 in (2,157.0 mm)	85.78 in (2,178.7 mm)	+0.85 in (+21.7 mm)	+1.00%
Revolutions per mile	746	739	−7	−0.99%

True speed with the speedometer calibrated for 255/40R19
Indicated	Actual on 255/40R19	Actual on 265/35R20	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.8 mph	+0.8 mph

Ride-height change: 265/35R20 raises the vehicle by 0.14 in (3.5 mm) at the axle (half the +6.9 mm diameter difference).

265/35R20 is 0.27 in taller than 255/40R19 and 10 mm wider, a 1.00% difference in overall diameter.

With the speedometer calibrated for 255/40R19, an indicated 60 mph is actually 60.6 mph on 265/35R20, and revolutions per mile change from 746 to 739.

265/35R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 255/40R19.

Size pages

Other comparisons with 255/40R19

Other comparisons with 265/35R20

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