Step 2. Find your measurement in the following table of typical axle diameters: 1.5-inch diameter, 1,000 pounds 1.75-inch diameter, 2,000 pounds 2.375-inch diameter, 3,500 pounds 3-inch diameter, 6,000 pounds 3.5-inch diameter, 8,000 pounds 4-inch diameter, 9,000 pounds 5-inch diameter, 10,000 pounds. Multiply the axle capacity in Step 2 by the