TireSizesFinder

185/70R13 vs 175/55R15

175/55R15 is 0.62 in (15.7 mm) shorter than 185/70R13, a −2.66% diameter difference. With the speedometer set for 185/70R13, an indicated 60 mph is 58.4 mph on 175/55R15.

Is this a safe swap?

Diameter difference −2.66%: within the ±3% guideline

By overall diameter alone, 175/55R15 falls inside the ±3% range commonly used as a guideline when replacing 185/70R13. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 185/70R13 (23.20 in) vs 175/55R15 (22.58 in)185/70R1323.20 in × 7.28 in175/55R1522.58 in × 6.89 in
Side profile and tread width, drawn to the same scale.
185/70R13 vs 175/55R15 differences
Measurement185/70R13175/55R15Difference% diff
Overall diameter23.20 in (589.2 mm)22.58 in (573.5 mm)−0.62 in (−15.7 mm)−2.66%
Sidewall height5.10 in (129.5 mm)3.79 in (96.3 mm)−1.31 in (−33.2 mm)−25.68%
Section width7.28 in (185.0 mm)6.89 in (175.0 mm)−0.39 in (−10.0 mm)−5.41%
Circumference72.88 in (1,851.0 mm)70.93 in (1,801.7 mm)−1.94 in (−49.3 mm)−2.66%
Revolutions per mile869893+24+2.74%
True speed with the speedometer calibrated for 185/70R13
IndicatedActual on 185/70R13Actual on 175/55R15Difference
30 mph30.0 mph29.2 mph−0.8 mph
60 mph60.0 mph58.4 mph−1.6 mph
75 mph75.0 mph73.0 mph−2.0 mph

Ride-height change: 175/55R15 lowers the vehicle by 0.31 in (7.9 mm) at the axle (half the −15.7 mm diameter difference).

175/55R15 is 0.62 in shorter than 185/70R13 and 10 mm narrower, a 2.66% difference in overall diameter.

With the speedometer calibrated for 185/70R13, an indicated 60 mph is actually 58.4 mph on 175/55R15, and revolutions per mile change from 869 to 893.

175/55R15 mounts on a 15-inch wheel, a plus-2 fitment from the 13-inch wheel of 185/70R13.

Size pages

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