TireSizesFinder

305/40R20 vs 285/35R22

285/35R22 is 0.25 in (6.3 mm) taller than 305/40R20, a +0.84% diameter difference. With the speedometer set for 305/40R20, an indicated 60 mph is 60.5 mph on 285/35R22.

Is this a safe swap?

Diameter difference +0.84%: under 1%

By overall diameter alone, 285/35R22 is a near match for 305/40R20; 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: 305/40R20 (29.61 in) vs 285/35R22 (29.85 in)305/40R2029.61 in × 12.01 in285/35R2229.85 in × 11.22 in
Side profile and tread width, drawn to the same scale.
305/40R20 vs 285/35R22 differences
Measurement305/40R20285/35R22Difference% diff
Overall diameter29.61 in (752.0 mm)29.85 in (758.3 mm)+0.25 in (+6.3 mm)+0.84%
Sidewall height4.80 in (122.0 mm)3.93 in (99.8 mm)−0.88 in (−22.2 mm)−18.24%
Section width12.01 in (305.0 mm)11.22 in (285.0 mm)−0.79 in (−20.0 mm)−6.56%
Circumference93.01 in (2,362.5 mm)93.79 in (2,382.3 mm)+0.78 in (+19.8 mm)+0.84%
Revolutions per mile681676−6−0.83%
True speed with the speedometer calibrated for 305/40R20
IndicatedActual on 305/40R20Actual on 285/35R22Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.5 mph+0.5 mph
75 mph75.0 mph75.6 mph+0.6 mph

Ride-height change: 285/35R22 raises the vehicle by 0.12 in (3.1 mm) at the axle (half the +6.3 mm diameter difference).

285/35R22 is 0.25 in taller than 305/40R20 and 20 mm narrower, a 0.84% difference in overall diameter.

With the speedometer calibrated for 305/40R20, an indicated 60 mph is actually 60.5 mph on 285/35R22, and revolutions per mile change from 681 to 676.

285/35R22 mounts on a 22-inch wheel, a plus-2 fitment from the 20-inch wheel of 305/40R20.

Size pages

Other comparisons with 305/40R20

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