185/60R16 vs 245/35R18

245/35R18 is 0.01 in (0.3 mm) taller than 185/60R16, a +0.05% diameter difference. With the speedometer set for 185/60R16, an indicated 60 mph is 60.0 mph on 245/35R18.

Is this a safe swap?

Diameter difference +0.05%: under 1%

By overall diameter alone, 245/35R18 is a near match for 185/60R16; 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.

185/60R16 vs 245/35R18 differences
Measurement	185/60R16	245/35R18	Difference	% diff
Overall diameter	24.74 in (628.4 mm)	24.75 in (628.7 mm)	+0.01 in (+0.3 mm)	+0.05%
Sidewall height	4.37 in (111.0 mm)	3.38 in (85.8 mm)	−0.99 in (−25.2 mm)	−22.75%
Section width	7.28 in (185.0 mm)	9.65 in (245.0 mm)	+2.36 in (+60.0 mm)	+32.43%
Circumference	77.72 in (1,974.2 mm)	77.76 in (1,975.1 mm)	+0.04 in (+0.9 mm)	+0.05%
Revolutions per mile	815	815	0	−0.05%

True speed with the speedometer calibrated for 185/60R16
Indicated	Actual on 185/60R16	Actual on 245/35R18
30 mph	30.0 mph	30.0 mph
60 mph	60.0 mph	60.0 mph
75 mph	75.0 mph	75.0 mph

Ride-height change: 245/35R18 raises the vehicle by 0.01 in (0.2 mm) at the axle (half the +0.3 mm diameter difference).

245/35R18 is 0.01 in taller than 185/60R16 and 60 mm wider, a 0.05% difference in overall diameter.

With the speedometer calibrated for 185/60R16, an indicated 60 mph is actually 60.0 mph on 245/35R18, and revolutions per mile change from 815 to 815.

245/35R18 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 245/35R18

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