235/50R17 vs 255/50R17

255/50R17 is 0.79 in (20.0 mm) taller than 235/50R17, a +3.00% diameter difference. With the speedometer set for 235/50R17, an indicated 60 mph is 61.8 mph on 255/50R17.

Is this a safe swap?

Diameter difference +3.00%: within the ±3% guideline

By overall diameter alone, 255/50R17 falls inside the ±3% range commonly used as a guideline when replacing 235/50R17. 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.

235/50R17 vs 255/50R17 differences
Measurement	235/50R17	255/50R17	Difference	% diff
Overall diameter	26.25 in (666.8 mm)	27.04 in (686.8 mm)	+0.79 in (+20.0 mm)	+3.00%
Sidewall height	4.63 in (117.5 mm)	5.02 in (127.5 mm)	+0.39 in (+10.0 mm)	+8.51%
Section width	9.25 in (235.0 mm)	10.04 in (255.0 mm)	+0.79 in (+20.0 mm)	+8.51%
Circumference	82.47 in (2,094.8 mm)	84.95 in (2,157.6 mm)	+2.47 in (+62.8 mm)	+3.00%
Revolutions per mile	768	746	−22	−2.91%

True speed with the speedometer calibrated for 235/50R17
Indicated	Actual on 235/50R17	Actual on 255/50R17	Difference
30 mph	30.0 mph	30.9 mph	+0.9 mph
60 mph	60.0 mph	61.8 mph	+1.8 mph
75 mph	75.0 mph	77.2 mph	+2.2 mph

Ride-height change: 255/50R17 raises the vehicle by 0.39 in (10.0 mm) at the axle (half the +20.0 mm diameter difference).

255/50R17 is 0.79 in taller than 235/50R17 and 20 mm wider, a 3.00% difference in overall diameter.

With the speedometer calibrated for 235/50R17, an indicated 60 mph is actually 61.8 mph on 255/50R17, and revolutions per mile change from 768 to 746.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 235/50R17

Other comparisons with 255/50R17

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