165/70R13 vs 185/55R15

185/55R15 is 0.92 in (23.3 mm) taller than 165/70R13, a +4.15% diameter difference. With the speedometer set for 165/70R13, an indicated 60 mph is 62.5 mph on 185/55R15.

Is this a safe swap?

Diameter difference +4.15%: outside the ±3% guideline

By overall diameter alone, 185/55R15 falls outside the ±3% range commonly used as a guideline when replacing 165/70R13; speedometer and ride-height changes are larger. 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.

165/70R13 vs 185/55R15 differences
Measurement	165/70R13	185/55R15	Difference	% diff
Overall diameter	22.09 in (561.2 mm)	23.01 in (584.5 mm)	+0.92 in (+23.3 mm)	+4.15%
Sidewall height	4.55 in (115.5 mm)	4.01 in (101.8 mm)	−0.54 in (−13.7 mm)	−11.90%
Section width	6.50 in (165.0 mm)	7.28 in (185.0 mm)	+0.79 in (+20.0 mm)	+12.12%
Circumference	69.41 in (1,763.1 mm)	72.29 in (1,836.3 mm)	+2.88 in (+73.2 mm)	+4.15%
Revolutions per mile	913	876	−36	−3.99%

True speed with the speedometer calibrated for 165/70R13
Indicated	Actual on 165/70R13	Actual on 185/55R15	Difference
30 mph	30.0 mph	31.2 mph	+1.2 mph
60 mph	60.0 mph	62.5 mph	+2.5 mph
75 mph	75.0 mph	78.1 mph	+3.1 mph

Ride-height change: 185/55R15 raises the vehicle by 0.46 in (11.6 mm) at the axle (half the +23.3 mm diameter difference).

185/55R15 is 0.92 in taller than 165/70R13 and 20 mm wider, a 4.15% difference in overall diameter.

With the speedometer calibrated for 165/70R13, an indicated 60 mph is actually 62.5 mph on 185/55R15, and revolutions per mile change from 913 to 876.

185/55R15 mounts on a 15-inch wheel, a plus-2 fitment from the 13-inch wheel of 165/70R13.

Size pages

Other comparisons with 165/70R13

Other comparisons with 185/55R15

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