245/40R17 vs 225/45R17

225/45R17 is 0.26 in (6.5 mm) taller than 245/40R17, a +1.04% diameter difference. With the speedometer set for 245/40R17, an indicated 60 mph is 60.6 mph on 225/45R17.

Is this a safe swap?

Diameter difference +1.04%: within the ±3% guideline

By overall diameter alone, 225/45R17 falls inside the ±3% range commonly used as a guideline when replacing 245/40R17. 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.

245/40R17 vs 225/45R17 differences
Measurement	245/40R17	225/45R17	Difference	% diff
Overall diameter	24.72 in (627.8 mm)	24.97 in (634.3 mm)	+0.26 in (+6.5 mm)	+1.04%
Sidewall height	3.86 in (98.0 mm)	3.99 in (101.3 mm)	+0.13 in (+3.3 mm)	+3.32%
Section width	9.65 in (245.0 mm)	8.86 in (225.0 mm)	−0.79 in (−20.0 mm)	−8.16%
Circumference	77.65 in (1,972.3 mm)	78.45 in (1,992.7 mm)	+0.80 in (+20.4 mm)	+1.04%
Revolutions per mile	816	808	−8	−1.02%

True speed with the speedometer calibrated for 245/40R17
Indicated	Actual on 245/40R17	Actual on 225/45R17	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.8 mph	+0.8 mph

Ride-height change: 225/45R17 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

225/45R17 is 0.26 in taller than 245/40R17 and 20 mm narrower, a 1.04% difference in overall diameter.

With the speedometer calibrated for 245/40R17, an indicated 60 mph is actually 60.6 mph on 225/45R17, and revolutions per mile change from 816 to 808.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 245/40R17

Other comparisons with 225/45R17

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