225/50R17 vs 255/45R17

255/45R17 is 0.18 in (4.5 mm) taller than 225/50R17, a +0.69% diameter difference. With the speedometer set for 225/50R17, an indicated 60 mph is 60.4 mph on 255/45R17.

Is this a safe swap?

Diameter difference +0.69%: under 1%

By overall diameter alone, 255/45R17 is a near match for 225/50R17; 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.

225/50R17 vs 255/45R17 differences
Measurement	225/50R17	255/45R17	Difference	% diff
Overall diameter	25.86 in (656.8 mm)	26.04 in (661.3 mm)	+0.18 in (+4.5 mm)	+0.69%
Sidewall height	4.43 in (112.5 mm)	4.52 in (114.8 mm)	+0.09 in (+2.3 mm)	+2.00%
Section width	8.86 in (225.0 mm)	10.04 in (255.0 mm)	+1.18 in (+30.0 mm)	+13.33%
Circumference	81.24 in (2,063.4 mm)	81.79 in (2,077.5 mm)	+0.56 in (+14.1 mm)	+0.69%
Revolutions per mile	780	775	−5	−0.68%

True speed with the speedometer calibrated for 225/50R17
Indicated	Actual on 225/50R17	Actual on 255/45R17	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.4 mph	+0.4 mph
75 mph	75.0 mph	75.5 mph	+0.5 mph

Ride-height change: 255/45R17 raises the vehicle by 0.09 in (2.3 mm) at the axle (half the +4.5 mm diameter difference).

255/45R17 is 0.18 in taller than 225/50R17 and 30 mm wider, a 0.69% difference in overall diameter.

With the speedometer calibrated for 225/50R17, an indicated 60 mph is actually 60.4 mph on 255/45R17, and revolutions per mile change from 780 to 775.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 225/50R17

Other comparisons with 255/45R17

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