TireSizesFinder

295/40R18 vs 225/40R20

225/40R20 is 0.20 in (5.2 mm) shorter than 295/40R18, a −0.75% diameter difference. With the speedometer set for 295/40R18, an indicated 60 mph is 59.5 mph on 225/40R20.

Is this a safe swap?

Diameter difference −0.75%: under 1%

By overall diameter alone, 225/40R20 is a near match for 295/40R18; 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: 295/40R18 (27.29 in) vs 225/40R20 (27.09 in)295/40R1827.29 in × 11.61 in225/40R2027.09 in × 8.86 in
Side profile and tread width, drawn to the same scale.
295/40R18 vs 225/40R20 differences
Measurement295/40R18225/40R20Difference% diff
Overall diameter27.29 in (693.2 mm)27.09 in (688.0 mm)−0.20 in (−5.2 mm)−0.75%
Sidewall height4.65 in (118.0 mm)3.54 in (90.0 mm)−1.10 in (−28.0 mm)−23.73%
Section width11.61 in (295.0 mm)8.86 in (225.0 mm)−2.76 in (−70.0 mm)−23.73%
Circumference85.74 in (2,177.8 mm)85.10 in (2,161.4 mm)−0.64 in (−16.3 mm)−0.75%
Revolutions per mile739745+6+0.76%
True speed with the speedometer calibrated for 295/40R18
IndicatedActual on 295/40R18Actual on 225/40R20Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.5 mph−0.5 mph
75 mph75.0 mph74.4 mph−0.6 mph

Ride-height change: 225/40R20 lowers the vehicle by 0.10 in (2.6 mm) at the axle (half the −5.2 mm diameter difference).

225/40R20 is 0.20 in shorter than 295/40R18 and 70 mm narrower, a 0.75% difference in overall diameter.

With the speedometer calibrated for 295/40R18, an indicated 60 mph is actually 59.5 mph on 225/40R20, and revolutions per mile change from 739 to 745.

225/40R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 295/40R18.

Size pages

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