205/50R16 vs 225/35R18

225/35R18 is 0.13 in (3.3 mm) taller than 205/50R16, a +0.54% diameter difference. With the speedometer set for 205/50R16, an indicated 60 mph is 60.3 mph on 225/35R18.

Is this a safe swap?

Diameter difference +0.54%: under 1%

By overall diameter alone, 225/35R18 is a near match for 205/50R16; 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.

205/50R16 vs 225/35R18 differences
Measurement	205/50R16	225/35R18	Difference	% diff
Overall diameter	24.07 in (611.4 mm)	24.20 in (614.7 mm)	+0.13 in (+3.3 mm)	+0.54%
Sidewall height	4.04 in (102.5 mm)	3.10 in (78.8 mm)	−0.94 in (−23.7 mm)	−23.17%
Section width	8.07 in (205.0 mm)	8.86 in (225.0 mm)	+0.79 in (+20.0 mm)	+9.76%
Circumference	75.62 in (1,920.8 mm)	76.03 in (1,931.1 mm)	+0.41 in (+10.4 mm)	+0.54%
Revolutions per mile	838	833	−4	−0.54%

True speed with the speedometer calibrated for 205/50R16
Indicated	Actual on 205/50R16	Actual on 225/35R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.3 mph	+0.3 mph
75 mph	75.0 mph	75.4 mph	+0.4 mph

Ride-height change: 225/35R18 raises the vehicle by 0.06 in (1.7 mm) at the axle (half the +3.3 mm diameter difference).

225/35R18 is 0.13 in taller than 205/50R16 and 20 mm wider, a 0.54% difference in overall diameter.

With the speedometer calibrated for 205/50R16, an indicated 60 mph is actually 60.3 mph on 225/35R18, and revolutions per mile change from 838 to 833.

225/35R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 205/50R16.

Size pages

Other comparisons with 205/50R16

Other comparisons with 225/35R18

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