TireSizesFinder

35x12.50R18 vs 325/60R20

325/60R20 is 0.35 in (9.0 mm) taller than 35x12.50R18, a +1.01% diameter difference. With the speedometer set for 35x12.50R18, an indicated 60 mph is 60.6 mph on 325/60R20.

Is this a safe swap?

Diameter difference +1.01%: within the ±3% guideline

By overall diameter alone, 325/60R20 falls inside the ±3% range commonly used as a guideline when replacing 35x12.50R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 35x12.50R18 (35.00 in) vs 325/60R20 (35.35 in)35x12.50R1835.00 in × 12.50 in325/60R2035.35 in × 12.80 in
Side profile and tread width, drawn to the same scale.
35x12.50R18 vs 325/60R20 differences
Measurement35x12.50R18325/60R20Difference% diff
Overall diameter35.00 in (889.0 mm)35.35 in (898.0 mm)+0.35 in (+9.0 mm)+1.01%
Sidewall height8.50 in (215.9 mm)7.68 in (195.0 mm)−0.82 in (−20.9 mm)−9.68%
Section width12.50 in (317.5 mm)12.80 in (325.0 mm)+0.30 in (+7.5 mm)+2.36%
Circumference109.96 in (2,792.9 mm)111.07 in (2,821.2 mm)+1.11 in (+28.3 mm)+1.01%
Revolutions per mile576570−6−1.00%
True speed with the speedometer calibrated for 35x12.50R18
IndicatedActual on 35x12.50R18Actual on 325/60R20Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.6 mph+0.6 mph
75 mph75.0 mph75.8 mph+0.8 mph

Ride-height change: 325/60R20 raises the vehicle by 0.18 in (4.5 mm) at the axle (half the +9.0 mm diameter difference).

325/60R20 is 0.35 in taller than 35x12.50R18 and 8 mm wider, a 1.01% difference in overall diameter.

With the speedometer calibrated for 35x12.50R18, an indicated 60 mph is actually 60.6 mph on 325/60R20, and revolutions per mile change from 576 to 570.

325/60R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 35x12.50R18.

Size pages

Other comparisons with 35x12.50R18

Other comparisons with 325/60R20

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.