TireSizesFinder

285/45R21 vs 285/40R22

285/40R22 is 0.12 in (3.1 mm) shorter than 285/45R21, a −0.39% diameter difference. With the speedometer set for 285/45R21, an indicated 60 mph is 59.8 mph on 285/40R22.

Is this a safe swap?

Diameter difference −0.39%: under 1%

By overall diameter alone, 285/40R22 is a near match for 285/45R21; 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: 285/45R21 (31.10 in) vs 285/40R22 (30.98 in)285/45R2131.10 in × 11.22 in285/40R2230.98 in × 11.22 in
Side profile and tread width, drawn to the same scale.
285/45R21 vs 285/40R22 differences
Measurement285/45R21285/40R22Difference% diff
Overall diameter31.10 in (789.9 mm)30.98 in (786.8 mm)−0.12 in (−3.1 mm)−0.39%
Sidewall height5.05 in (128.3 mm)4.49 in (114.0 mm)−0.56 in (−14.2 mm)−11.11%
Section width11.22 in (285.0 mm)11.22 in (285.0 mm)0.00 in (0.0 mm)0.00%
Circumference97.70 in (2,481.5 mm)97.32 in (2,471.8 mm)−0.38 in (−9.7 mm)−0.39%
Revolutions per mile649651+3+0.39%
True speed with the speedometer calibrated for 285/45R21
IndicatedActual on 285/45R21Actual on 285/40R22Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.8 mph−0.2 mph
75 mph75.0 mph74.7 mph−0.3 mph

Ride-height change: 285/40R22 lowers the vehicle by 0.06 in (1.6 mm) at the axle (half the −3.1 mm diameter difference).

285/40R22 is 0.12 in shorter than 285/45R21 and the same width, a 0.39% difference in overall diameter.

With the speedometer calibrated for 285/45R21, an indicated 60 mph is actually 59.8 mph on 285/40R22, and revolutions per mile change from 649 to 651.

285/40R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 285/45R21.

Size pages

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