315/60R20 vs 325/45R22

325/45R22 is 1.37 in (34.7 mm) shorter than 315/60R20, a −3.92% diameter difference. With the speedometer set for 315/60R20, an indicated 60 mph is 57.7 mph on 325/45R22.

Is this a safe swap?

Diameter difference −3.92%: outside the ±3% guideline

By overall diameter alone, 325/45R22 falls outside the ±3% range commonly used as a guideline when replacing 315/60R20; speedometer and ride-height changes are larger. 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.

315/60R20 vs 325/45R22 differences
Measurement	315/60R20	325/45R22	Difference	% diff
Overall diameter	34.88 in (886.0 mm)	33.52 in (851.3 mm)	−1.37 in (−34.7 mm)	−3.92%
Sidewall height	7.44 in (189.0 mm)	5.76 in (146.3 mm)	−1.68 in (−42.7 mm)	−22.62%
Section width	12.40 in (315.0 mm)	12.80 in (325.0 mm)	+0.39 in (+10.0 mm)	+3.17%
Circumference	109.58 in (2,783.5 mm)	105.29 in (2,674.4 mm)	−4.29 in (−109.0 mm)	−3.92%
Revolutions per mile	578	602	+24	+4.08%

True speed with the speedometer calibrated for 315/60R20
Indicated	Actual on 315/60R20	Actual on 325/45R22	Difference
30 mph	30.0 mph	28.8 mph	−1.2 mph
60 mph	60.0 mph	57.7 mph	−2.3 mph
75 mph	75.0 mph	72.1 mph	−2.9 mph

Ride-height change: 325/45R22 lowers the vehicle by 0.68 in (17.4 mm) at the axle (half the −34.7 mm diameter difference).

325/45R22 is 1.37 in shorter than 315/60R20 and 10 mm wider, a 3.92% difference in overall diameter.

With the speedometer calibrated for 315/60R20, an indicated 60 mph is actually 57.7 mph on 325/45R22, and revolutions per mile change from 578 to 602.

325/45R22 mounts on a 22-inch wheel, a plus-2 fitment from the 20-inch wheel of 315/60R20.

Size pages

Other comparisons with 315/60R20

Other comparisons with 325/45R22

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