315/60R20 vs 325/60R20

325/60R20 is 0.47 in (12.0 mm) taller than 315/60R20, a +1.35% diameter difference. With the speedometer set for 315/60R20, an indicated 60 mph is 60.8 mph on 325/60R20.

Is this a safe swap?

Diameter difference +1.35%: within the ±3% guideline

By overall diameter alone, 325/60R20 falls inside the ±3% range commonly used as a guideline when replacing 315/60R20. 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 325/60R20 differences
Measurement	315/60R20	325/60R20	Difference	% diff
Overall diameter	34.88 in (886.0 mm)	35.35 in (898.0 mm)	+0.47 in (+12.0 mm)	+1.35%
Sidewall height	7.44 in (189.0 mm)	7.68 in (195.0 mm)	+0.24 in (+6.0 mm)	+3.17%
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)	111.07 in (2,821.2 mm)	+1.48 in (+37.7 mm)	+1.35%
Revolutions per mile	578	570	−8	−1.34%

True speed with the speedometer calibrated for 315/60R20
Indicated	Actual on 315/60R20	Actual on 325/60R20	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: 325/60R20 raises the vehicle by 0.24 in (6.0 mm) at the axle (half the +12.0 mm diameter difference).

325/60R20 is 0.47 in taller than 315/60R20 and 10 mm wider, a 1.35% difference in overall diameter.

With the speedometer calibrated for 315/60R20, an indicated 60 mph is actually 60.8 mph on 325/60R20, and revolutions per mile change from 578 to 570.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 315/60R20

Other comparisons with 325/60R20

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