195/45R17 vs 225/35R18

225/35R18 is 0.29 in (7.4 mm) taller than 195/45R17, a +1.22% diameter difference. With the speedometer set for 195/45R17, an indicated 60 mph is 60.7 mph on 225/35R18.

Is this a safe swap?

Diameter difference +1.22%: within the ±3% guideline

By overall diameter alone, 225/35R18 falls inside the ±3% range commonly used as a guideline when replacing 195/45R17. 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.

195/45R17 vs 225/35R18 differences
Measurement	195/45R17	225/35R18	Difference	% diff
Overall diameter	23.91 in (607.3 mm)	24.20 in (614.7 mm)	+0.29 in (+7.4 mm)	+1.22%
Sidewall height	3.45 in (87.8 mm)	3.10 in (78.8 mm)	−0.35 in (−9.0 mm)	−10.26%
Section width	7.68 in (195.0 mm)	8.86 in (225.0 mm)	+1.18 in (+30.0 mm)	+15.38%
Circumference	75.11 in (1,907.9 mm)	76.03 in (1,931.1 mm)	+0.92 in (+23.2 mm)	+1.22%
Revolutions per mile	844	833	−10	−1.20%

True speed with the speedometer calibrated for 195/45R17
Indicated	Actual on 195/45R17	Actual on 225/35R18	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.7 mph	+0.7 mph
75 mph	75.0 mph	75.9 mph	+0.9 mph

Ride-height change: 225/35R18 raises the vehicle by 0.15 in (3.7 mm) at the axle (half the +7.4 mm diameter difference).

225/35R18 is 0.29 in taller than 195/45R17 and 30 mm wider, a 1.22% difference in overall diameter.

With the speedometer calibrated for 195/45R17, an indicated 60 mph is actually 60.7 mph on 225/35R18, and revolutions per mile change from 844 to 833.

225/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 195/45R17.

Size pages

Other comparisons with 195/45R17

Other comparisons with 225/35R18

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