175/55R15 vs 225/40R16

225/40R16 is 0.51 in (12.9 mm) taller than 175/55R15, a +2.25% diameter difference. With the speedometer set for 175/55R15, an indicated 60 mph is 61.3 mph on 225/40R16.

Is this a safe swap?

Diameter difference +2.25%: within the ±3% guideline

By overall diameter alone, 225/40R16 falls inside the ±3% range commonly used as a guideline when replacing 175/55R15. 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.

175/55R15 vs 225/40R16 differences
Measurement	175/55R15	225/40R16	Difference	% diff
Overall diameter	22.58 in (573.5 mm)	23.09 in (586.4 mm)	+0.51 in (+12.9 mm)	+2.25%
Sidewall height	3.79 in (96.3 mm)	3.54 in (90.0 mm)	−0.25 in (−6.2 mm)	−6.49%
Section width	6.89 in (175.0 mm)	8.86 in (225.0 mm)	+1.97 in (+50.0 mm)	+28.57%
Circumference	70.93 in (1,801.7 mm)	72.53 in (1,842.2 mm)	+1.60 in (+40.5 mm)	+2.25%
Revolutions per mile	893	874	−20	−2.20%

True speed with the speedometer calibrated for 175/55R15
Indicated	Actual on 175/55R15	Actual on 225/40R16	Difference
30 mph	30.0 mph	30.7 mph	+0.7 mph
60 mph	60.0 mph	61.3 mph	+1.3 mph
75 mph	75.0 mph	76.7 mph	+1.7 mph

Ride-height change: 225/40R16 raises the vehicle by 0.25 in (6.4 mm) at the axle (half the +12.9 mm diameter difference).

225/40R16 is 0.51 in taller than 175/55R15 and 50 mm wider, a 2.25% difference in overall diameter.

With the speedometer calibrated for 175/55R15, an indicated 60 mph is actually 61.3 mph on 225/40R16, and revolutions per mile change from 893 to 874.

225/40R16 mounts on a 16-inch wheel, a plus-1 fitment from the 15-inch wheel of 175/55R15.

Size pages

Other comparisons with 175/55R15

Other comparisons with 225/40R16

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