175/60R15 vs 185/60R15

185/60R15 is 0.47 in (12.0 mm) taller than 175/60R15, a +2.03% diameter difference. With the speedometer set for 175/60R15, an indicated 60 mph is 61.2 mph on 185/60R15.

Is this a safe swap?

Diameter difference +2.03%: within the ±3% guideline

By overall diameter alone, 185/60R15 falls inside the ±3% range commonly used as a guideline when replacing 175/60R15. 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.

175/60R15 vs 185/60R15 differences
Measurement	175/60R15	185/60R15	Difference	% diff
Overall diameter	23.27 in (591.0 mm)	23.74 in (603.0 mm)	+0.47 in (+12.0 mm)	+2.03%
Sidewall height	4.13 in (105.0 mm)	4.37 in (111.0 mm)	+0.24 in (+6.0 mm)	+5.71%
Section width	6.89 in (175.0 mm)	7.28 in (185.0 mm)	+0.39 in (+10.0 mm)	+5.71%
Circumference	73.10 in (1,856.7 mm)	74.58 in (1,894.4 mm)	+1.48 in (+37.7 mm)	+2.03%
Revolutions per mile	867	850	−17	−1.99%

True speed with the speedometer calibrated for 175/60R15
Indicated	Actual on 175/60R15	Actual on 185/60R15	Difference
30 mph	30.0 mph	30.6 mph	+0.6 mph
60 mph	60.0 mph	61.2 mph	+1.2 mph
75 mph	75.0 mph	76.5 mph	+1.5 mph

Ride-height change: 185/60R15 raises the vehicle by 0.24 in (6.0 mm) at the axle (half the +12.0 mm diameter difference).

185/60R15 is 0.47 in taller than 175/60R15 and 10 mm wider, a 2.03% difference in overall diameter.

With the speedometer calibrated for 175/60R15, an indicated 60 mph is actually 61.2 mph on 185/60R15, and revolutions per mile change from 867 to 850.

Both sizes mount on 15-inch wheels.

Size pages

Other comparisons with 175/60R15

Other comparisons with 185/60R15

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