255/45R20 vs 315/30R22

315/30R22 is 0.41 in (10.3 mm) taller than 255/45R20, a +1.40% diameter difference. With the speedometer set for 255/45R20, an indicated 60 mph is 60.8 mph on 315/30R22.

Is this a safe swap?

Diameter difference +1.40%: within the ±3% guideline

By overall diameter alone, 315/30R22 falls inside the ±3% range commonly used as a guideline when replacing 255/45R20. 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.

255/45R20 vs 315/30R22 differences
Measurement	255/45R20	315/30R22	Difference	% diff
Overall diameter	29.04 in (737.5 mm)	29.44 in (747.8 mm)	+0.41 in (+10.3 mm)	+1.40%
Sidewall height	4.52 in (114.8 mm)	3.72 in (94.5 mm)	−0.80 in (−20.2 mm)	−17.65%
Section width	10.04 in (255.0 mm)	12.40 in (315.0 mm)	+2.36 in (+60.0 mm)	+23.53%
Circumference	91.22 in (2,316.9 mm)	92.49 in (2,349.3 mm)	+1.27 in (+32.4 mm)	+1.40%
Revolutions per mile	695	685	−10	−1.38%

True speed with the speedometer calibrated for 255/45R20
Indicated	Actual on 255/45R20	Actual on 315/30R22	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.8 mph	+0.8 mph
75 mph	75.0 mph	76.0 mph	+1.0 mph

Ride-height change: 315/30R22 raises the vehicle by 0.20 in (5.1 mm) at the axle (half the +10.3 mm diameter difference).

315/30R22 is 0.41 in taller than 255/45R20 and 60 mm wider, a 1.40% difference in overall diameter.

With the speedometer calibrated for 255/45R20, an indicated 60 mph is actually 60.8 mph on 315/30R22, and revolutions per mile change from 695 to 685.

315/30R22 mounts on a 22-inch wheel, a plus-2 fitment from the 20-inch wheel of 255/45R20.

Size pages

Other comparisons with 255/45R20

Other comparisons with 315/30R22

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