TireSizesFinder

255/55R19 vs 235/55R20

235/55R20 is 0.13 in (3.4 mm) taller than 255/55R19, a +0.45% diameter difference. With the speedometer set for 255/55R19, an indicated 60 mph is 60.3 mph on 235/55R20.

Is this a safe swap?

Diameter difference +0.45%: under 1%

By overall diameter alone, 235/55R20 is a near match for 255/55R19; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 255/55R19 (30.04 in) vs 235/55R20 (30.18 in)255/55R1930.04 in × 10.04 in235/55R2030.18 in × 9.25 in
Side profile and tread width, drawn to the same scale.
255/55R19 vs 235/55R20 differences
Measurement255/55R19235/55R20Difference% diff
Overall diameter30.04 in (763.1 mm)30.18 in (766.5 mm)+0.13 in (+3.4 mm)+0.45%
Sidewall height5.52 in (140.3 mm)5.09 in (129.3 mm)−0.43 in (−11.0 mm)−7.84%
Section width10.04 in (255.0 mm)9.25 in (235.0 mm)−0.79 in (−20.0 mm)−7.84%
Circumference94.38 in (2,397.3 mm)94.80 in (2,408.0 mm)+0.42 in (+10.7 mm)+0.45%
Revolutions per mile671668−3−0.44%
True speed with the speedometer calibrated for 255/55R19
IndicatedActual on 255/55R19Actual on 235/55R20Difference
30 mph30.0 mph30.1 mph+0.1 mph
60 mph60.0 mph60.3 mph+0.3 mph
75 mph75.0 mph75.3 mph+0.3 mph

Ride-height change: 235/55R20 raises the vehicle by 0.07 in (1.7 mm) at the axle (half the +3.4 mm diameter difference).

235/55R20 is 0.13 in taller than 255/55R19 and 20 mm narrower, a 0.45% difference in overall diameter.

With the speedometer calibrated for 255/55R19, an indicated 60 mph is actually 60.3 mph on 235/55R20, and revolutions per mile change from 671 to 668.

235/55R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 255/55R19.

Size pages

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Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.