Abstract: Improved third, tag, axle for a standard two-axle log-carrying trailer to permit carrying additional load. The inventive third axle assembly is pivotally linked directly to the bunk of a standard log trailer bogie by two, laterally-spaced hitch assemblies that permit vertical motion of the third axle, but not lateral movement. The inventive third axle assembly increases the payload capacity of the trailer with better maneuverability. A pivoting cone support and centering assembly is used to insure proper alignment of the tag axle during transport and when first unloaded. By following the bunk, the inventive axle more closely follows the tractor front wheel path during turns, rather than worsening the cut-across effect of ordinary turn geometry. That is, the inventive tag axle tracks more nearly in the proper lane, tending significantly less to cut across inside the tractor turn in both left and right turns, and thus is a safer rig.