185/60R16 vs 235/35R18

235/35R18 is 0.26 in (6.7 mm) shorter than 185/60R16, a −1.07% diameter difference. With the speedometer set for 185/60R16, an indicated 60 mph is 59.4 mph on 235/35R18.

Is this a safe swap?

Diameter difference −1.07%: within the ±3% guideline

By overall diameter alone, 235/35R18 falls inside the ±3% range commonly used as a guideline when replacing 185/60R16. 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.

185/60R16 vs 235/35R18 differences
Measurement	185/60R16	235/35R18	Difference	% diff
Overall diameter	24.74 in (628.4 mm)	24.48 in (621.7 mm)	−0.26 in (−6.7 mm)	−1.07%
Sidewall height	4.37 in (111.0 mm)	3.24 in (82.3 mm)	−1.13 in (−28.7 mm)	−25.90%
Section width	7.28 in (185.0 mm)	9.25 in (235.0 mm)	+1.97 in (+50.0 mm)	+27.03%
Circumference	77.72 in (1,974.2 mm)	76.89 in (1,953.1 mm)	−0.83 in (−21.0 mm)	−1.07%
Revolutions per mile	815	824	+9	+1.08%

True speed with the speedometer calibrated for 185/60R16
Indicated	Actual on 185/60R16	Actual on 235/35R18	Difference
30 mph	30.0 mph	29.7 mph	−0.3 mph
60 mph	60.0 mph	59.4 mph	−0.6 mph
75 mph	75.0 mph	74.2 mph	−0.8 mph

Ride-height change: 235/35R18 lowers the vehicle by 0.13 in (3.3 mm) at the axle (half the −6.7 mm diameter difference).

235/35R18 is 0.26 in shorter than 185/60R16 and 50 mm wider, a 1.07% difference in overall diameter.

With the speedometer calibrated for 185/60R16, an indicated 60 mph is actually 59.4 mph on 235/35R18, and revolutions per mile change from 815 to 824.

235/35R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 185/60R16.

Size pages

Other comparisons with 185/60R16

Other comparisons with 235/35R18

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