185/55R15 vs 225/40R16

225/40R16 is 0.07 in (1.9 mm) taller than 185/55R15, a +0.33% diameter difference. With the speedometer set for 185/55R15, an indicated 60 mph is 60.2 mph on 225/40R16.

Is this a safe swap?

Diameter difference +0.33%: under 1%

By overall diameter alone, 225/40R16 is a near match for 185/55R15; 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.

185/55R15 vs 225/40R16 differences
Measurement	185/55R15	225/40R16	Difference	% diff
Overall diameter	23.01 in (584.5 mm)	23.09 in (586.4 mm)	+0.07 in (+1.9 mm)	+0.33%
Sidewall height	4.01 in (101.8 mm)	3.54 in (90.0 mm)	−0.46 in (−11.7 mm)	−11.55%
Section width	7.28 in (185.0 mm)	8.86 in (225.0 mm)	+1.57 in (+40.0 mm)	+21.62%
Circumference	72.29 in (1,836.3 mm)	72.53 in (1,842.2 mm)	+0.24 in (+6.0 mm)	+0.33%
Revolutions per mile	876	874	−3	−0.32%

True speed with the speedometer calibrated for 185/55R15
Indicated	Actual on 185/55R15	Actual on 225/40R16	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 225/40R16 raises the vehicle by 0.04 in (0.9 mm) at the axle (half the +1.9 mm diameter difference).

225/40R16 is 0.07 in taller than 185/55R15 and 40 mm wider, a 0.33% difference in overall diameter.

With the speedometer calibrated for 185/55R15, an indicated 60 mph is actually 60.2 mph on 225/40R16, and revolutions per mile change from 876 to 874.

225/40R16 mounts on a 16-inch wheel, a plus-1 fitment from the 15-inch wheel of 185/55R15.

Size pages

Other comparisons with 185/55R15

Other comparisons with 225/40R16

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