255/50R17 vs 235/55R17

235/55R17 is 0.14 in (3.5 mm) taller than 255/50R17, a +0.51% diameter difference. With the speedometer set for 255/50R17, an indicated 60 mph is 60.3 mph on 235/55R17.

Is this a safe swap?

Diameter difference +0.51%: under 1%

By overall diameter alone, 235/55R17 is a near match for 255/50R17; the speedometer changes by less than 1%. 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.

255/50R17 vs 235/55R17 differences
Measurement	255/50R17	235/55R17	Difference	% diff
Overall diameter	27.04 in (686.8 mm)	27.18 in (690.3 mm)	+0.14 in (+3.5 mm)	+0.51%
Sidewall height	5.02 in (127.5 mm)	5.09 in (129.3 mm)	+0.07 in (+1.8 mm)	+1.37%
Section width	10.04 in (255.0 mm)	9.25 in (235.0 mm)	−0.79 in (−20.0 mm)	−7.84%
Circumference	84.95 in (2,157.6 mm)	85.38 in (2,168.6 mm)	+0.43 in (+11.0 mm)	+0.51%
Revolutions per mile	746	742	−4	−0.51%

True speed with the speedometer calibrated for 255/50R17
Indicated	Actual on 255/50R17	Actual on 235/55R17	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.3 mph	+0.3 mph
75 mph	75.0 mph	75.4 mph	+0.4 mph

Ride-height change: 235/55R17 raises the vehicle by 0.07 in (1.8 mm) at the axle (half the +3.5 mm diameter difference).

235/55R17 is 0.14 in taller than 255/50R17 and 20 mm narrower, a 0.51% difference in overall diameter.

With the speedometer calibrated for 255/50R17, an indicated 60 mph is actually 60.3 mph on 235/55R17, and revolutions per mile change from 746 to 742.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 255/50R17

Other comparisons with 235/55R17

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