Why I Am Replacing the Leaf Spring Mounting Plates

Below is a picture of my driver's side rear leaf spring mounting plate.  The post sticking out is where the bottom end of the shock absorber goes.  Note the gigantic welt.  Can't imagine what would cause that.  No way I am putting this back on.  The suspension rebuild kit doesn't include replacements, so I get to buy these separately.  Cost about $15 each.