215/45R17 vs 225/35R18

225/35R18 is 0.42 in (10.6 mm) shorter than 215/45R17, a −1.70% diameter difference. With the speedometer set for 215/45R17, an indicated 60 mph is 59.0 mph on 225/35R18.

Is this a safe swap?

Diameter difference −1.70%: within the ±3% guideline

By overall diameter alone, 225/35R18 falls inside the ±3% range commonly used as a guideline when replacing 215/45R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

215/45R17 vs 225/35R18 differences
Measurement	215/45R17	225/35R18	Difference	% diff
Overall diameter	24.62 in (625.3 mm)	24.20 in (614.7 mm)	−0.42 in (−10.6 mm)	−1.70%
Sidewall height	3.81 in (96.8 mm)	3.10 in (78.8 mm)	−0.71 in (−18.0 mm)	−18.60%
Section width	8.46 in (215.0 mm)	8.86 in (225.0 mm)	+0.39 in (+10.0 mm)	+4.65%
Circumference	77.34 in (1,964.4 mm)	76.03 in (1,931.1 mm)	−1.31 in (−33.3 mm)	−1.70%
Revolutions per mile	819	833	+14	+1.72%

True speed with the speedometer calibrated for 215/45R17
Indicated	Actual on 215/45R17	Actual on 225/35R18	Difference
30 mph	30.0 mph	29.5 mph	−0.5 mph
60 mph	60.0 mph	59.0 mph	−1.0 mph
75 mph	75.0 mph	73.7 mph	−1.3 mph

Ride-height change: 225/35R18 lowers the vehicle by 0.21 in (5.3 mm) at the axle (half the −10.6 mm diameter difference).

225/35R18 is 0.42 in shorter than 215/45R17 and 10 mm wider, a 1.70% difference in overall diameter.

With the speedometer calibrated for 215/45R17, an indicated 60 mph is actually 59.0 mph on 225/35R18, and revolutions per mile change from 819 to 833.

225/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 215/45R17.

Size pages

Other comparisons with 215/45R17

Other comparisons with 225/35R18

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.