TireSizesFinder

205/55R15 vs 205/40R17

205/40R17 is 0.42 in (10.7 mm) shorter than 205/55R15, a −1.76% diameter difference. With the speedometer set for 205/55R15, an indicated 60 mph is 58.9 mph on 205/40R17.

Is this a safe swap?

Diameter difference −1.76%: within the ±3% guideline

By overall diameter alone, 205/40R17 falls inside the ±3% range commonly used as a guideline when replacing 205/55R15. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 205/55R15 (23.88 in) vs 205/40R17 (23.46 in)205/55R1523.88 in × 8.07 in205/40R1723.46 in × 8.07 in
Side profile and tread width, drawn to the same scale.
205/55R15 vs 205/40R17 differences
Measurement205/55R15205/40R17Difference% diff
Overall diameter23.88 in (606.5 mm)23.46 in (595.8 mm)−0.42 in (−10.7 mm)−1.76%
Sidewall height4.44 in (112.8 mm)3.23 in (82.0 mm)−1.21 in (−30.7 mm)−27.27%
Section width8.07 in (205.0 mm)8.07 in (205.0 mm)0.00 in (0.0 mm)0.00%
Circumference75.01 in (1,905.4 mm)73.69 in (1,871.8 mm)−1.32 in (−33.6 mm)−1.76%
Revolutions per mile845860+15+1.80%
True speed with the speedometer calibrated for 205/55R15
IndicatedActual on 205/55R15Actual on 205/40R17Difference
30 mph30.0 mph29.5 mph−0.5 mph
60 mph60.0 mph58.9 mph−1.1 mph
75 mph75.0 mph73.7 mph−1.3 mph

Ride-height change: 205/40R17 lowers the vehicle by 0.21 in (5.4 mm) at the axle (half the −10.7 mm diameter difference).

205/40R17 is 0.42 in shorter than 205/55R15 and the same width, a 1.76% difference in overall diameter.

With the speedometer calibrated for 205/55R15, an indicated 60 mph is actually 58.9 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 205/55R15.

Size pages

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Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.