TireSizesFinder

215/40R17 vs 225/35R18

225/35R18 is 0.43 in (10.9 mm) taller than 215/40R17, a +1.81% diameter difference. With the speedometer set for 215/40R17, an indicated 60 mph is 61.1 mph on 225/35R18.

Is this a safe swap?

Diameter difference +1.81%: within the ±3% guideline

By overall diameter alone, 225/35R18 falls inside the ±3% range commonly used as a guideline when replacing 215/40R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 215/40R17 (23.77 in) vs 225/35R18 (24.20 in)215/40R1723.77 in × 8.46 in225/35R1824.20 in × 8.86 in
Side profile and tread width, drawn to the same scale.
215/40R17 vs 225/35R18 differences
Measurement215/40R17225/35R18Difference% diff
Overall diameter23.77 in (603.8 mm)24.20 in (614.7 mm)+0.43 in (+10.9 mm)+1.81%
Sidewall height3.39 in (86.0 mm)3.10 in (78.8 mm)−0.29 in (−7.2 mm)−8.43%
Section width8.46 in (215.0 mm)8.86 in (225.0 mm)+0.39 in (+10.0 mm)+4.65%
Circumference74.68 in (1,896.9 mm)76.03 in (1,931.1 mm)+1.35 in (+34.2 mm)+1.81%
Revolutions per mile848833−15−1.77%
True speed with the speedometer calibrated for 215/40R17
IndicatedActual on 215/40R17Actual on 225/35R18Difference
30 mph30.0 mph30.5 mph+0.5 mph
60 mph60.0 mph61.1 mph+1.1 mph
75 mph75.0 mph76.4 mph+1.4 mph

Ride-height change: 225/35R18 raises the vehicle by 0.21 in (5.5 mm) at the axle (half the +10.9 mm diameter difference).

225/35R18 is 0.43 in taller than 215/40R17 and 10 mm wider, a 1.81% difference in overall diameter.

With the speedometer calibrated for 215/40R17, an indicated 60 mph is actually 61.1 mph on 225/35R18, and revolutions per mile change from 848 to 833.

225/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 215/40R17.

Size pages

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