305/55R20 vs 325/45R22

325/45R22 is 0.31 in (7.8 mm) taller than 305/55R20, a +0.92% diameter difference. With the speedometer set for 305/55R20, an indicated 60 mph is 60.6 mph on 325/45R22.

Is this a safe swap?

Diameter difference +0.92%: under 1%

By overall diameter alone, 325/45R22 is a near match for 305/55R20; 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.

305/55R20 vs 325/45R22 differences
Measurement	305/55R20	325/45R22	Difference	% diff
Overall diameter	33.21 in (843.5 mm)	33.52 in (851.3 mm)	+0.31 in (+7.8 mm)	+0.92%
Sidewall height	6.60 in (167.8 mm)	5.76 in (146.3 mm)	−0.85 in (−21.5 mm)	−12.82%
Section width	12.01 in (305.0 mm)	12.80 in (325.0 mm)	+0.79 in (+20.0 mm)	+6.56%
Circumference	104.33 in (2,649.9 mm)	105.29 in (2,674.4 mm)	+0.96 in (+24.5 mm)	+0.92%
Revolutions per mile	607	602	−6	−0.92%

True speed with the speedometer calibrated for 305/55R20
Indicated	Actual on 305/55R20	Actual on 325/45R22	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	75.7 mph	+0.7 mph

Ride-height change: 325/45R22 raises the vehicle by 0.15 in (3.9 mm) at the axle (half the +7.8 mm diameter difference).

325/45R22 is 0.31 in taller than 305/55R20 and 20 mm wider, a 0.92% difference in overall diameter.

With the speedometer calibrated for 305/55R20, an indicated 60 mph is actually 60.6 mph on 325/45R22, and revolutions per mile change from 607 to 602.

325/45R22 mounts on a 22-inch wheel, a plus-2 fitment from the 20-inch wheel of 305/55R20.

Size pages

Other comparisons with 305/55R20

Other comparisons with 325/45R22

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