Drag link

A drag link converts rotary motion from a crank to a second crank or link in a different plane or axis.

The term is commonly used in automotive technology for the link in a four bar steering linkage that converts rotation of a steering arm to a center link and eventually to tie rod links which pivot the wheels to be steered. A drag link is used when the steering arm operates in a plane above the other links. The drag link converts the sweeping arc of the steering arm to linear motion in the plane of the other steering links.

Typically, one end of the drag link is connected via the Pitman arm and steering gearbox to the steering wheel (providing the connection between the driver and the steering system); the other end is attached to the vehicle frame by the idler arm.

An alternate steering mechanism is a rack and pinion, a three bar linkage that eliminates the drag link by directly moving the center link.

The length of a drag link can affect the geometry and thus the steering ratio. Severe wear of this part can affect the wheel alignment such as Toe-in or Toe-out settings. This can drastically affect the handling and stability of the vehicle at speed.