235/70R16 vs 225/60R18

225/60R18 is 0.32 in (8.2 mm) shorter than 235/70R16, a −1.12% diameter difference. With the speedometer set for 235/70R16, an indicated 60 mph is 59.3 mph on 225/60R18.

Is this a safe swap?

Diameter difference −1.12%: within the ±3% guideline

By overall diameter alone, 225/60R18 falls inside the ±3% range commonly used as a guideline when replacing 235/70R16. 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.

235/70R16 vs 225/60R18 differences
Measurement	235/70R16	225/60R18	Difference	% diff
Overall diameter	28.95 in (735.4 mm)	28.63 in (727.2 mm)	−0.32 in (−8.2 mm)	−1.12%
Sidewall height	6.48 in (164.5 mm)	5.31 in (135.0 mm)	−1.16 in (−29.5 mm)	−17.93%
Section width	9.25 in (235.0 mm)	8.86 in (225.0 mm)	−0.39 in (−10.0 mm)	−4.26%
Circumference	90.96 in (2,310.3 mm)	89.94 in (2,284.6 mm)	−1.01 in (−25.8 mm)	−1.12%
Revolutions per mile	697	704	+8	+1.13%

True speed with the speedometer calibrated for 235/70R16
Indicated	Actual on 235/70R16	Actual on 225/60R18	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.3 mph	−0.7 mph
75 mph	75.0 mph	74.2 mph	−0.8 mph

Ride-height change: 225/60R18 lowers the vehicle by 0.16 in (4.1 mm) at the axle (half the −8.2 mm diameter difference).

225/60R18 is 0.32 in shorter than 235/70R16 and 10 mm narrower, a 1.12% difference in overall diameter.

With the speedometer calibrated for 235/70R16, an indicated 60 mph is actually 59.3 mph on 225/60R18, and revolutions per mile change from 697 to 704.

225/60R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 235/70R16.

Size pages

Other comparisons with 235/70R16

Other comparisons with 225/60R18

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