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

Steering

Steering is the term applied to the collection of components, linkages, etc. which will allow a vessel or vehicle to follow the desired course...

 linkage that converts rotation of a steering arm to a center link and eventually to tie rod

Tie rod

A tie rod is a slender structural unit used as a tie and capable of carrying tensile loads only.- Subtypes and examples of applications :* In airplane structures, tie rods are sometimes used in the fuselage or wings....

 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

Pitman arm

The Pitman arm is a steering component in an automobile or truck.The Pitman arm is a linkage attached to the steering gear sector shaft, that converts the angular motion of the sector shaft into the linear motion needed to steer the wheels. The Pitman arm is supported by the sector shaft and...

 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

Idler arm

On an automobile or truck with a conventional Parallelogram steering linkage, the Idler Arm or idler arm assembly is a pivoting support for the steering linkage....

.

An alternate steering mechanism is a rack and pinion

Rack and pinion

A rack and pinion is a type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion. A circular gear called "the pinion" engages teeth on a linear "gear" bar called "the rack"; rotational motion applied to the pinion causes the rack to move, thereby...

, 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

Steering ratio

Steering ratio refers to the ratio between the turn of the steering wheel or handlebars and the turn of the wheels .The steering ratio, is the amount of degrees you have to turn the steering wheel, for the wheels to turn an amount of degrees.In motorcycles and bicycles, the steering ratio is...

. Severe wear of this part can affect the wheel alignment such as Toe

Toe (automotive)

In automotive engineering, toe, also known as tracking, is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic and compliant effects. This can be contrasted with steer, which is the antisymmetric angle, i.e. both...

-in or Toe-out settings. This can drastically affect the handling and stability of the vehicle at speed.