205/70R15 vs 205/55R17

205/55R17 is 0.42 in (10.7 mm) shorter than 205/70R15, a −1.60% diameter difference. With the speedometer set for 205/70R15, an indicated 60 mph is 59.0 mph on 205/55R17.

Is this a safe swap?

Diameter difference −1.60%: within the ±3% guideline

By overall diameter alone, 205/55R17 falls inside the ±3% range commonly used as a guideline when replacing 205/70R15. 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.

205/70R15 vs 205/55R17 differences
Measurement	205/70R15	205/55R17	Difference	% diff
Overall diameter	26.30 in (668.0 mm)	25.88 in (657.3 mm)	−0.42 in (−10.7 mm)	−1.60%
Sidewall height	5.65 in (143.5 mm)	4.44 in (112.8 mm)	−1.21 in (−30.7 mm)	−21.43%
Section width	8.07 in (205.0 mm)	8.07 in (205.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	82.62 in (2,098.6 mm)	81.30 in (2,065.0 mm)	−1.32 in (−33.6 mm)	−1.60%
Revolutions per mile	767	779	+12	+1.63%

True speed with the speedometer calibrated for 205/70R15
Indicated	Actual on 205/70R15	Actual on 205/55R17	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	73.8 mph	−1.2 mph

Ride-height change: 205/55R17 lowers the vehicle by 0.21 in (5.4 mm) at the axle (half the −10.7 mm diameter difference).

205/55R17 is 0.42 in shorter than 205/70R15 and the same width, a 1.60% difference in overall diameter.

With the speedometer calibrated for 205/70R15, an indicated 60 mph is actually 59.0 mph on 205/55R17, and revolutions per mile change from 767 to 779.

205/55R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 205/70R15.

Size pages

Other comparisons with 205/70R15

Other comparisons with 205/55R17

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