165/65R15 vs 225/40R16

225/40R16 is 0.36 in (9.1 mm) shorter than 165/65R15, a −1.53% diameter difference. With the speedometer set for 165/65R15, an indicated 60 mph is 59.1 mph on 225/40R16.

Is this a safe swap?

Diameter difference −1.53%: within the ±3% guideline

By overall diameter alone, 225/40R16 falls inside the ±3% range commonly used as a guideline when replacing 165/65R15. 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.

165/65R15 vs 225/40R16 differences
Measurement	165/65R15	225/40R16	Difference	% diff
Overall diameter	23.44 in (595.5 mm)	23.09 in (586.4 mm)	−0.36 in (−9.1 mm)	−1.53%
Sidewall height	4.22 in (107.3 mm)	3.54 in (90.0 mm)	−0.68 in (−17.2 mm)	−16.08%
Section width	6.50 in (165.0 mm)	8.86 in (225.0 mm)	+2.36 in (+60.0 mm)	+36.36%
Circumference	73.65 in (1,870.8 mm)	72.53 in (1,842.2 mm)	−1.13 in (−28.6 mm)	−1.53%
Revolutions per mile	860	874	+13	+1.55%

True speed with the speedometer calibrated for 165/65R15
Indicated	Actual on 165/65R15	Actual on 225/40R16	Difference
30 mph	30.0 mph	29.5 mph	−0.5 mph
60 mph	60.0 mph	59.1 mph	−0.9 mph
75 mph	75.0 mph	73.9 mph	−1.1 mph

Ride-height change: 225/40R16 lowers the vehicle by 0.18 in (4.6 mm) at the axle (half the −9.1 mm diameter difference).

225/40R16 is 0.36 in shorter than 165/65R15 and 60 mm wider, a 1.53% difference in overall diameter.

With the speedometer calibrated for 165/65R15, an indicated 60 mph is actually 59.1 mph on 225/40R16, and revolutions per mile change from 860 to 874.

225/40R16 mounts on a 16-inch wheel, a plus-1 fitment from the 15-inch wheel of 165/65R15.

Size pages

Other comparisons with 165/65R15

Other comparisons with 225/40R16

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