205/45R17 vs 225/35R18

225/35R18 is 0.06 in (1.6 mm) shorter than 205/45R17, a −0.26% diameter difference. With the speedometer set for 205/45R17, an indicated 60 mph is 59.8 mph on 225/35R18.

Is this a safe swap?

Diameter difference −0.26%: under 1%

By overall diameter alone, 225/35R18 is a near match for 205/45R17; the speedometer changes by less than 1%. 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.

205/45R17 vs 225/35R18 differences
Measurement	205/45R17	225/35R18	Difference	% diff
Overall diameter	24.26 in (616.3 mm)	24.20 in (614.7 mm)	−0.06 in (−1.6 mm)	−0.26%
Sidewall height	3.63 in (92.3 mm)	3.10 in (78.8 mm)	−0.53 in (−13.5 mm)	−14.63%
Section width	8.07 in (205.0 mm)	8.86 in (225.0 mm)	+0.79 in (+20.0 mm)	+9.76%
Circumference	76.23 in (1,936.2 mm)	76.03 in (1,931.1 mm)	−0.20 in (−5.0 mm)	−0.26%
Revolutions per mile	831	833	+2	+0.26%

True speed with the speedometer calibrated for 205/45R17
Indicated	Actual on 205/45R17	Actual on 225/35R18	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.8 mph	−0.2 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 225/35R18 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.6 mm diameter difference).

225/35R18 is 0.06 in shorter than 205/45R17 and 20 mm wider, a 0.26% difference in overall diameter.

With the speedometer calibrated for 205/45R17, an indicated 60 mph is actually 59.8 mph on 225/35R18, and revolutions per mile change from 831 to 833.

225/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 205/45R17.

Size pages

Other comparisons with 205/45R17

Other comparisons with 225/35R18

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