TireSizesFinder

265/40R17 vs 225/40R18

225/40R18 is 0.26 in (6.6 mm) shorter than 265/40R17, a −1.03% diameter difference. With the speedometer set for 265/40R17, an indicated 60 mph is 59.4 mph on 225/40R18.

Is this a safe swap?

Diameter difference −1.03%: within the ±3% guideline

By overall diameter alone, 225/40R18 falls inside the ±3% range commonly used as a guideline when replacing 265/40R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 265/40R17 (25.35 in) vs 225/40R18 (25.09 in)265/40R1725.35 in × 10.43 in225/40R1825.09 in × 8.86 in
Side profile and tread width, drawn to the same scale.
265/40R17 vs 225/40R18 differences
Measurement265/40R17225/40R18Difference% diff
Overall diameter25.35 in (643.8 mm)25.09 in (637.2 mm)−0.26 in (−6.6 mm)−1.03%
Sidewall height4.17 in (106.0 mm)3.54 in (90.0 mm)−0.63 in (−16.0 mm)−15.09%
Section width10.43 in (265.0 mm)8.86 in (225.0 mm)−1.57 in (−40.0 mm)−15.09%
Circumference79.63 in (2,022.6 mm)78.81 in (2,001.8 mm)−0.82 in (−20.7 mm)−1.03%
Revolutions per mile796804+8+1.04%
True speed with the speedometer calibrated for 265/40R17
IndicatedActual on 265/40R17Actual on 225/40R18Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.2 mph−0.8 mph

Ride-height change: 225/40R18 lowers the vehicle by 0.13 in (3.3 mm) at the axle (half the −6.6 mm diameter difference).

225/40R18 is 0.26 in shorter than 265/40R17 and 40 mm narrower, a 1.03% difference in overall diameter.

With the speedometer calibrated for 265/40R17, an indicated 60 mph is actually 59.4 mph on 225/40R18, and revolutions per mile change from 796 to 804.

225/40R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 265/40R17.

Size pages

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