TireSizesFinder

265/40R18 vs 225/35R20

225/35R20 is 0.15 in (3.7 mm) shorter than 265/40R18, a −0.55% diameter difference. With the speedometer set for 265/40R18, an indicated 60 mph is 59.7 mph on 225/35R20.

Is this a safe swap?

Diameter difference −0.55%: under 1%

By overall diameter alone, 225/35R20 is a near match for 265/40R18; 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: 265/40R18 (26.35 in) vs 225/35R20 (26.20 in)265/40R1826.35 in × 10.43 in225/35R2026.20 in × 8.86 in
Side profile and tread width, drawn to the same scale.
265/40R18 vs 225/35R20 differences
Measurement265/40R18225/35R20Difference% diff
Overall diameter26.35 in (669.2 mm)26.20 in (665.5 mm)−0.15 in (−3.7 mm)−0.55%
Sidewall height4.17 in (106.0 mm)3.10 in (78.8 mm)−1.07 in (−27.2 mm)−25.71%
Section width10.43 in (265.0 mm)8.86 in (225.0 mm)−1.57 in (−40.0 mm)−15.09%
Circumference82.77 in (2,102.4 mm)82.31 in (2,090.7 mm)−0.46 in (−11.6 mm)−0.55%
Revolutions per mile765770+4+0.56%
True speed with the speedometer calibrated for 265/40R18
IndicatedActual on 265/40R18Actual on 225/35R20Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.7 mph−0.3 mph
75 mph75.0 mph74.6 mph−0.4 mph

Ride-height change: 225/35R20 lowers the vehicle by 0.07 in (1.9 mm) at the axle (half the −3.7 mm diameter difference).

225/35R20 is 0.15 in shorter than 265/40R18 and 40 mm narrower, a 0.55% difference in overall diameter.

With the speedometer calibrated for 265/40R18, an indicated 60 mph is actually 59.7 mph on 225/35R20, and revolutions per mile change from 765 to 770.

225/35R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 265/40R18.

Size pages

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