TireSizesFinder

285/40R21 vs 255/40R22

255/40R22 is 0.06 in (1.4 mm) taller than 285/40R21, a +0.18% diameter difference. With the speedometer set for 285/40R21, an indicated 60 mph is 60.1 mph on 255/40R22.

Is this a safe swap?

Diameter difference +0.18%: under 1%

By overall diameter alone, 255/40R22 is a near match for 285/40R21; 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: 285/40R21 (29.98 in) vs 255/40R22 (30.03 in)285/40R2129.98 in × 11.22 in255/40R2230.03 in × 10.04 in
Side profile and tread width, drawn to the same scale.
285/40R21 vs 255/40R22 differences
Measurement285/40R21255/40R22Difference% diff
Overall diameter29.98 in (761.4 mm)30.03 in (762.8 mm)+0.06 in (+1.4 mm)+0.18%
Sidewall height4.49 in (114.0 mm)4.02 in (102.0 mm)−0.47 in (−12.0 mm)−10.53%
Section width11.22 in (285.0 mm)10.04 in (255.0 mm)−1.18 in (−30.0 mm)−10.53%
Circumference94.17 in (2,392.0 mm)94.35 in (2,396.4 mm)+0.17 in (+4.4 mm)+0.18%
Revolutions per mile673672−1−0.18%
True speed with the speedometer calibrated for 285/40R21
IndicatedActual on 285/40R21Actual on 255/40R22Difference
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: 255/40R22 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.4 mm diameter difference).

255/40R22 is 0.06 in taller than 285/40R21 and 30 mm narrower, a 0.18% difference in overall diameter.

With the speedometer calibrated for 285/40R21, an indicated 60 mph is actually 60.1 mph on 255/40R22, and revolutions per mile change from 673 to 672.

255/40R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 285/40R21.

Size pages

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Other comparisons with 255/40R22

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