TireSizesFinder

255/40R20 vs 255/30R22

255/30R22 is 0.01 in (0.2 mm) shorter than 255/40R20, a −0.03% diameter difference. With the speedometer set for 255/40R20, an indicated 60 mph is 60.0 mph on 255/30R22.

Is this a safe swap?

Diameter difference −0.03%: under 1%

By overall diameter alone, 255/30R22 is a near match for 255/40R20; 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: 255/40R20 (28.03 in) vs 255/30R22 (28.02 in)255/40R2028.03 in × 10.04 in255/30R2228.02 in × 10.04 in
Side profile and tread width, drawn to the same scale.
255/40R20 vs 255/30R22 differences
Measurement255/40R20255/30R22Difference% diff
Overall diameter28.03 in (712.0 mm)28.02 in (711.8 mm)−0.01 in (−0.2 mm)−0.03%
Sidewall height4.02 in (102.0 mm)3.01 in (76.5 mm)−1.00 in (−25.5 mm)−25.00%
Section width10.04 in (255.0 mm)10.04 in (255.0 mm)0.00 in (0.0 mm)0.00%
Circumference88.06 in (2,236.8 mm)88.04 in (2,236.2 mm)−0.02 in (−0.6 mm)−0.03%
Revolutions per mile7197200+0.03%
True speed with the speedometer calibrated for 255/40R20
IndicatedActual on 255/40R20Actual on 255/30R22Difference
30 mph30.0 mph30.0 mph0.0 mph
60 mph60.0 mph60.0 mph0.0 mph
75 mph75.0 mph75.0 mph0.0 mph

Ride-height change: 255/30R22 lowers the vehicle by 0.00 in (0.1 mm) at the axle (half the −0.2 mm diameter difference).

255/30R22 is 0.01 in shorter than 255/40R20 and the same width, a 0.03% difference in overall diameter.

With the speedometer calibrated for 255/40R20, an indicated 60 mph is actually 60.0 mph on 255/30R22, and revolutions per mile change from 719 to 720.

255/30R22 mounts on a 22-inch wheel, a plus-2 fitment from the 20-inch wheel of 255/40R20.

Size pages

Other comparisons with 255/40R20

Other comparisons with 255/30R22

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