175/55R15 vs 205/50R15

205/50R15 is 0.49 in (12.5 mm) taller than 175/55R15, a +2.18% diameter difference. With the speedometer set for 175/55R15, an indicated 60 mph is 61.3 mph on 205/50R15.

Is this a safe swap?

Diameter difference +2.18%: within the ±3% guideline

By overall diameter alone, 205/50R15 falls inside the ±3% range commonly used as a guideline when replacing 175/55R15. 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.

175/55R15 vs 205/50R15 differences
Measurement	175/55R15	205/50R15	Difference	% diff
Overall diameter	22.58 in (573.5 mm)	23.07 in (586.0 mm)	+0.49 in (+12.5 mm)	+2.18%
Sidewall height	3.79 in (96.3 mm)	4.04 in (102.5 mm)	+0.25 in (+6.3 mm)	+6.49%
Section width	6.89 in (175.0 mm)	8.07 in (205.0 mm)	+1.18 in (+30.0 mm)	+17.14%
Circumference	70.93 in (1,801.7 mm)	72.48 in (1,841.0 mm)	+1.55 in (+39.3 mm)	+2.18%
Revolutions per mile	893	874	−19	−2.13%

True speed with the speedometer calibrated for 175/55R15
Indicated	Actual on 175/55R15	Actual on 205/50R15	Difference
30 mph	30.0 mph	30.7 mph	+0.7 mph
60 mph	60.0 mph	61.3 mph	+1.3 mph
75 mph	75.0 mph	76.6 mph	+1.6 mph

Ride-height change: 205/50R15 raises the vehicle by 0.25 in (6.3 mm) at the axle (half the +12.5 mm diameter difference).

205/50R15 is 0.49 in taller than 175/55R15 and 30 mm wider, a 2.18% difference in overall diameter.

With the speedometer calibrated for 175/55R15, an indicated 60 mph is actually 61.3 mph on 205/50R15, and revolutions per mile change from 893 to 874.

Both sizes mount on 15-inch wheels.

Size pages

Other comparisons with 175/55R15

Other comparisons with 205/50R15

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