TireSizesFinder

185/70R13 vs 185/55R15

185/55R15 is 0.19 in (4.7 mm) shorter than 185/70R13, a −0.80% diameter difference. With the speedometer set for 185/70R13, an indicated 60 mph is 59.5 mph on 185/55R15.

Is this a safe swap?

Diameter difference −0.80%: under 1%

By overall diameter alone, 185/55R15 is a near match for 185/70R13; the speedometer changes by less than 1%. 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 185/55R15 (23.01 in)185/70R1323.20 in × 7.28 in185/55R1523.01 in × 7.28 in
Side profile and tread width, drawn to the same scale.
185/70R13 vs 185/55R15 differences
Measurement185/70R13185/55R15Difference% diff
Overall diameter23.20 in (589.2 mm)23.01 in (584.5 mm)−0.19 in (−4.7 mm)−0.80%
Sidewall height5.10 in (129.5 mm)4.01 in (101.8 mm)−1.09 in (−27.7 mm)−21.43%
Section width7.28 in (185.0 mm)7.28 in (185.0 mm)0.00 in (0.0 mm)0.00%
Circumference72.88 in (1,851.0 mm)72.29 in (1,836.3 mm)−0.58 in (−14.8 mm)−0.80%
Revolutions per mile869876+7+0.80%
True speed with the speedometer calibrated for 185/70R13
IndicatedActual on 185/70R13Actual on 185/55R15Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.5 mph−0.5 mph
75 mph75.0 mph74.4 mph−0.6 mph

Ride-height change: 185/55R15 lowers the vehicle by 0.09 in (2.4 mm) at the axle (half the −4.7 mm diameter difference).

185/55R15 is 0.19 in shorter than 185/70R13 and the same width, a 0.80% difference in overall diameter.

With the speedometer calibrated for 185/70R13, an indicated 60 mph is actually 59.5 mph on 185/55R15, and revolutions per mile change from 869 to 876.

185/55R15 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.