Definitions for "Tag axle"
Keywords:  axle, rear, nonpowered, rearmost, dead
a dead axle situated behind a drive axle
In a group of rear axles, the forward-most axle is a driving type and the rearmost axle is a free rolling (load carrying only) commonly called "dead axle."
Extra axle fitted behind the drive axle of a tractor unit or rigid vehicle. Can usually be lifted clear of the road when not required.