225/50R15 vs 205/40R17

205/40R17 is 0.40 in (10.2 mm) shorter than 225/50R15, a −1.68% diameter difference. With the speedometer set for 225/50R15, an indicated 60 mph is 59.0 mph on 205/40R17.

Is this a safe swap?

Diameter difference −1.68%: within the ±3% guideline

By overall diameter alone, 205/40R17 falls inside the ±3% range commonly used as a guideline when replacing 225/50R15. 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.

225/50R15 vs 205/40R17 differences
Measurement	225/50R15	205/40R17	Difference	% diff
Overall diameter	23.86 in (606.0 mm)	23.46 in (595.8 mm)	−0.40 in (−10.2 mm)	−1.68%
Sidewall height	4.43 in (112.5 mm)	3.23 in (82.0 mm)	−1.20 in (−30.5 mm)	−27.11%
Section width	8.86 in (225.0 mm)	8.07 in (205.0 mm)	−0.79 in (−20.0 mm)	−8.89%
Circumference	74.95 in (1,903.8 mm)	73.69 in (1,871.8 mm)	−1.26 in (−32.0 mm)	−1.68%
Revolutions per mile	845	860	+14	+1.71%

True speed with the speedometer calibrated for 225/50R15
Indicated	Actual on 225/50R15	Actual on 205/40R17	Difference
30 mph	30.0 mph	29.5 mph	−0.5 mph
60 mph	60.0 mph	59.0 mph	−1.0 mph
75 mph	75.0 mph	73.7 mph	−1.3 mph

Ride-height change: 205/40R17 lowers the vehicle by 0.20 in (5.1 mm) at the axle (half the −10.2 mm diameter difference).

205/40R17 is 0.40 in shorter than 225/50R15 and 20 mm narrower, a 1.68% difference in overall diameter.

With the speedometer calibrated for 225/50R15, an indicated 60 mph is actually 59.0 mph on 205/40R17, and revolutions per mile change from 845 to 860.

205/40R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 225/50R15.

Size pages

Other comparisons with 225/50R15

Other comparisons with 205/40R17

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