TireSizesFinder

235/55R20 vs 255/40R22

255/40R22 is 0.15 in (3.7 mm) shorter than 235/55R20, a −0.48% diameter difference. With the speedometer set for 235/55R20, an indicated 60 mph is 59.7 mph on 255/40R22.

Is this a safe swap?

Diameter difference −0.48%: under 1%

By overall diameter alone, 255/40R22 is a near match for 235/55R20; 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: 235/55R20 (30.18 in) vs 255/40R22 (30.03 in)235/55R2030.18 in × 9.25 in255/40R2230.03 in × 10.04 in
Side profile and tread width, drawn to the same scale.
235/55R20 vs 255/40R22 differences
Measurement235/55R20255/40R22Difference% diff
Overall diameter30.18 in (766.5 mm)30.03 in (762.8 mm)−0.15 in (−3.7 mm)−0.48%
Sidewall height5.09 in (129.3 mm)4.02 in (102.0 mm)−1.07 in (−27.2 mm)−21.08%
Section width9.25 in (235.0 mm)10.04 in (255.0 mm)+0.79 in (+20.0 mm)+8.51%
Circumference94.80 in (2,408.0 mm)94.35 in (2,396.4 mm)−0.46 in (−11.6 mm)−0.48%
Revolutions per mile668672+3+0.49%
True speed with the speedometer calibrated for 235/55R20
IndicatedActual on 235/55R20Actual on 255/40R22Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.7 mph−0.3 mph
75 mph75.0 mph74.6 mph−0.4 mph

Ride-height change: 255/40R22 lowers the vehicle by 0.07 in (1.9 mm) at the axle (half the −3.7 mm diameter difference).

255/40R22 is 0.15 in shorter than 235/55R20 and 20 mm wider, a 0.48% difference in overall diameter.

With the speedometer calibrated for 235/55R20, an indicated 60 mph is actually 59.7 mph on 255/40R22, and revolutions per mile change from 668 to 672.

255/40R22 mounts on a 22-inch wheel, a plus-2 fitment from the 20-inch wheel of 235/55R20.

Size pages

Other comparisons with 235/55R20

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