305/55R20 vs 325/50R22

325/50R22 is 1.59 in (40.3 mm) taller than 305/55R20, a +4.78% diameter difference. With the speedometer set for 305/55R20, an indicated 60 mph is 62.9 mph on 325/50R22.

Is this a safe swap?

Diameter difference +4.78%: outside the ±3% guideline

By overall diameter alone, 325/50R22 falls outside the ±3% range commonly used as a guideline when replacing 305/55R20; 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.

305/55R20 vs 325/50R22 differences
Measurement	305/55R20	325/50R22	Difference	% diff
Overall diameter	33.21 in (843.5 mm)	34.80 in (883.8 mm)	+1.59 in (+40.3 mm)	+4.78%
Sidewall height	6.60 in (167.8 mm)	6.40 in (162.5 mm)	−0.21 in (−5.2 mm)	−3.13%
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)	109.31 in (2,776.5 mm)	+4.98 in (+126.6 mm)	+4.78%
Revolutions per mile	607	580	−28	−4.56%

True speed with the speedometer calibrated for 305/55R20
Indicated	Actual on 305/55R20	Actual on 325/50R22	Difference
30 mph	30.0 mph	31.4 mph	+1.4 mph
60 mph	60.0 mph	62.9 mph	+2.9 mph
75 mph	75.0 mph	78.6 mph	+3.6 mph

Ride-height change: 325/50R22 raises the vehicle by 0.79 in (20.1 mm) at the axle (half the +40.3 mm diameter difference).

325/50R22 is 1.59 in taller than 305/55R20 and 20 mm wider, a 4.78% difference in overall diameter.

With the speedometer calibrated for 305/55R20, an indicated 60 mph is actually 62.9 mph on 325/50R22, and revolutions per mile change from 607 to 580.

325/50R22 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 325/50R22

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