185/55R16 vs 225/40R17

225/40R17 is 0.07 in (1.9 mm) taller than 185/55R16, a +0.31% diameter difference. With the speedometer set for 185/55R16, an indicated 60 mph is 60.2 mph on 225/40R17.

Is this a safe swap?

Diameter difference +0.31%: under 1%

By overall diameter alone, 225/40R17 is a near match for 185/55R16; 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.

185/55R16 vs 225/40R17 differences
Measurement	185/55R16	225/40R17	Difference	% diff
Overall diameter	24.01 in (609.9 mm)	24.09 in (611.8 mm)	+0.07 in (+1.9 mm)	+0.31%
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	75.44 in (1,916.1 mm)	75.67 in (1,922.0 mm)	+0.24 in (+6.0 mm)	+0.31%
Revolutions per mile	840	837	−3	−0.31%

True speed with the speedometer calibrated for 185/55R16
Indicated	Actual on 185/55R16	Actual on 225/40R17	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: 225/40R17 raises the vehicle by 0.04 in (0.9 mm) at the axle (half the +1.9 mm diameter difference).

225/40R17 is 0.07 in taller than 185/55R16 and 40 mm wider, a 0.31% difference in overall diameter.

With the speedometer calibrated for 185/55R16, an indicated 60 mph is actually 60.2 mph on 225/40R17, and revolutions per mile change from 840 to 837.

225/40R17 mounts on a 17-inch wheel, a plus-1 fitment from the 16-inch wheel of 185/55R16.

Size pages

Other comparisons with 185/55R16

Other comparisons with 225/40R17

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