TireSizesFinder

255/55R19 vs 285/45R20

285/45R20 is 0.06 in (1.4 mm) taller than 255/55R19, a +0.18% diameter difference. With the speedometer set for 255/55R19, an indicated 60 mph is 60.1 mph on 285/45R20.

Is this a safe swap?

Diameter difference +0.18%: under 1%

By overall diameter alone, 285/45R20 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 285/45R20 (30.10 in)255/55R1930.04 in × 10.04 in285/45R2030.10 in × 11.22 in
Side profile and tread width, drawn to the same scale.
255/55R19 vs 285/45R20 differences
Measurement255/55R19285/45R20Difference% diff
Overall diameter30.04 in (763.1 mm)30.10 in (764.5 mm)+0.06 in (+1.4 mm)+0.18%
Sidewall height5.52 in (140.3 mm)5.05 in (128.3 mm)−0.47 in (−12.0 mm)−8.56%
Section width10.04 in (255.0 mm)11.22 in (285.0 mm)+1.18 in (+30.0 mm)+11.76%
Circumference94.38 in (2,397.3 mm)94.56 in (2,401.7 mm)+0.17 in (+4.4 mm)+0.18%
Revolutions per mile671670−1−0.18%
True speed with the speedometer calibrated for 255/55R19
IndicatedActual on 255/55R19Actual on 285/45R20Difference
30 mph30.0 mph30.1 mph+0.1 mph
60 mph60.0 mph60.1 mph+0.1 mph
75 mph75.0 mph75.1 mph+0.1 mph

Ride-height change: 285/45R20 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.4 mm diameter difference).

285/45R20 is 0.06 in taller than 255/55R19 and 30 mm wider, a 0.18% difference in overall diameter.

With the speedometer calibrated for 255/55R19, an indicated 60 mph is actually 60.1 mph on 285/45R20, and revolutions per mile change from 671 to 670.

285/45R20 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.