225/50R16 vs 245/35R18

245/35R18 is 0.11 in (2.7 mm) shorter than 225/50R16, a −0.43% diameter difference. With the speedometer set for 225/50R16, an indicated 60 mph is 59.7 mph on 245/35R18.

Is this a safe swap?

Diameter difference −0.43%: under 1%

By overall diameter alone, 245/35R18 is a near match for 225/50R16; 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.

225/50R16 vs 245/35R18 differences
Measurement	225/50R16	245/35R18	Difference	% diff
Overall diameter	24.86 in (631.4 mm)	24.75 in (628.7 mm)	−0.11 in (−2.7 mm)	−0.43%
Sidewall height	4.43 in (112.5 mm)	3.38 in (85.8 mm)	−1.05 in (−26.7 mm)	−23.78%
Section width	8.86 in (225.0 mm)	9.65 in (245.0 mm)	+0.79 in (+20.0 mm)	+8.89%
Circumference	78.09 in (1,983.6 mm)	77.76 in (1,975.1 mm)	−0.33 in (−8.5 mm)	−0.43%
Revolutions per mile	811	815	+3	+0.43%

True speed with the speedometer calibrated for 225/50R16
Indicated	Actual on 225/50R16	Actual on 245/35R18	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.7 mph	−0.3 mph
75 mph	75.0 mph	74.7 mph	−0.3 mph

Ride-height change: 245/35R18 lowers the vehicle by 0.05 in (1.3 mm) at the axle (half the −2.7 mm diameter difference).

245/35R18 is 0.11 in shorter than 225/50R16 and 20 mm wider, a 0.43% difference in overall diameter.

With the speedometer calibrated for 225/50R16, an indicated 60 mph is actually 59.7 mph on 245/35R18, and revolutions per mile change from 811 to 815.

245/35R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 225/50R16.

Size pages

Other comparisons with 225/50R16

Other comparisons with 245/35R18

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