195/50R15 vs 185/55R15

185/55R15 is 0.33 in (8.5 mm) taller than 195/50R15, a +1.48% diameter difference. With the speedometer set for 195/50R15, an indicated 60 mph is 60.9 mph on 185/55R15.

Is this a safe swap?

Diameter difference +1.48%: within the ±3% guideline

By overall diameter alone, 185/55R15 falls inside the ±3% range commonly used as a guideline when replacing 195/50R15. 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.

195/50R15 vs 185/55R15 differences
Measurement	195/50R15	185/55R15	Difference	% diff
Overall diameter	22.68 in (576.0 mm)	23.01 in (584.5 mm)	+0.33 in (+8.5 mm)	+1.48%
Sidewall height	3.84 in (97.5 mm)	4.01 in (101.8 mm)	+0.17 in (+4.3 mm)	+4.36%
Section width	7.68 in (195.0 mm)	7.28 in (185.0 mm)	−0.39 in (−10.0 mm)	−5.13%
Circumference	71.24 in (1,809.6 mm)	72.29 in (1,836.3 mm)	+1.05 in (+26.7 mm)	+1.48%
Revolutions per mile	889	876	−13	−1.45%

True speed with the speedometer calibrated for 195/50R15
Indicated	Actual on 195/50R15	Actual on 185/55R15	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.9 mph	+0.9 mph
75 mph	75.0 mph	76.1 mph	+1.1 mph

Ride-height change: 185/55R15 raises the vehicle by 0.17 in (4.3 mm) at the axle (half the +8.5 mm diameter difference).

185/55R15 is 0.33 in taller than 195/50R15 and 10 mm narrower, a 1.48% difference in overall diameter.

With the speedometer calibrated for 195/50R15, an indicated 60 mph is actually 60.9 mph on 185/55R15, and revolutions per mile change from 889 to 876.

Both sizes mount on 15-inch wheels.

Size pages

Other comparisons with 195/50R15

Other comparisons with 185/55R15

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