255/45R17 vs 235/50R17

235/50R17 is 0.22 in (5.5 mm) taller than 255/45R17, a +0.83% diameter difference. With the speedometer set for 255/45R17, an indicated 60 mph is 60.5 mph on 235/50R17.

Is this a safe swap?

Diameter difference +0.83%: under 1%

By overall diameter alone, 235/50R17 is a near match for 255/45R17; 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.

255/45R17 vs 235/50R17 differences
Measurement	255/45R17	235/50R17	Difference	% diff
Overall diameter	26.04 in (661.3 mm)	26.25 in (666.8 mm)	+0.22 in (+5.5 mm)	+0.83%
Sidewall height	4.52 in (114.8 mm)	4.63 in (117.5 mm)	+0.11 in (+2.8 mm)	+2.40%
Section width	10.04 in (255.0 mm)	9.25 in (235.0 mm)	−0.79 in (−20.0 mm)	−7.84%
Circumference	81.79 in (2,077.5 mm)	82.47 in (2,094.8 mm)	+0.68 in (+17.3 mm)	+0.83%
Revolutions per mile	775	768	−6	−0.82%

True speed with the speedometer calibrated for 255/45R17
Indicated	Actual on 255/45R17	Actual on 235/50R17	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 235/50R17 raises the vehicle by 0.11 in (2.8 mm) at the axle (half the +5.5 mm diameter difference).

235/50R17 is 0.22 in taller than 255/45R17 and 20 mm narrower, a 0.83% difference in overall diameter.

With the speedometer calibrated for 255/45R17, an indicated 60 mph is actually 60.5 mph on 235/50R17, and revolutions per mile change from 775 to 768.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 255/45R17

Other comparisons with 235/50R17

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