TireSizesFinder

265/70R18 vs 285/55R20

285/55R20 is 0.26 in (6.7 mm) shorter than 265/70R18, a −0.81% diameter difference. With the speedometer set for 265/70R18, an indicated 60 mph is 59.5 mph on 285/55R20.

Is this a safe swap?

Diameter difference −0.81%: under 1%

By overall diameter alone, 285/55R20 is a near match for 265/70R18; 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: 265/70R18 (32.61 in) vs 285/55R20 (32.34 in)265/70R1832.61 in × 10.43 in285/55R2032.34 in × 11.22 in
Side profile and tread width, drawn to the same scale.
265/70R18 vs 285/55R20 differences
Measurement265/70R18285/55R20Difference% diff
Overall diameter32.61 in (828.2 mm)32.34 in (821.5 mm)−0.26 in (−6.7 mm)−0.81%
Sidewall height7.30 in (185.5 mm)6.17 in (156.8 mm)−1.13 in (−28.7 mm)−15.50%
Section width10.43 in (265.0 mm)11.22 in (285.0 mm)+0.79 in (+20.0 mm)+7.55%
Circumference102.44 in (2,601.9 mm)101.61 in (2,580.8 mm)−0.83 in (−21.0 mm)−0.81%
Revolutions per mile619624+5+0.82%
True speed with the speedometer calibrated for 265/70R18
IndicatedActual on 265/70R18Actual on 285/55R20Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.5 mph−0.5 mph
75 mph75.0 mph74.4 mph−0.6 mph

Ride-height change: 285/55R20 lowers the vehicle by 0.13 in (3.4 mm) at the axle (half the −6.7 mm diameter difference).

285/55R20 is 0.26 in shorter than 265/70R18 and 20 mm wider, a 0.81% difference in overall diameter.

With the speedometer calibrated for 265/70R18, an indicated 60 mph is actually 59.5 mph on 285/55R20, and revolutions per mile change from 619 to 624.

285/55R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 265/70R18.

Size pages

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