Our fifth wheel came with 5100 lb axles--loaded with our normal personal possessions and fresh water, the two axles weigh 10,220 lbs. So, they were loaded right up to the limit and probably ready to bend at the slightest abuse. We upgraded to 6,000 lb axles and disc brakes. OP might want to consider upgrading to a heavier wall tube. Dexter makes 3 wall thicknesses of 3" axle tubes ranging from 5100 to 7000 lb axles. RV manufacturers are going to use the cheapest, thinnest, axle tubes rated for what they're building.