Have you ever wondered how it is possible for you to barely turn the steering wheel on your vehicle and the vehicle instantly and easily changes directions and provides you with a sense of control and safety? There are many components responsible for this, and the steering linkage is a primary one.
The term “steering linkage” applies to the system of pivots and connecting parts placed between the steering gear and the steering arms attached to the front or rear wheels. The steering linkage transfers the motion of the steering gear output shaft to the steering arms that turn the wheels to maneuver and control vehicle direction.
Components used in the steering linkage depend on the type of steering gear used in the vehicle. There are basically two types of steering gears used today. The rack and pinion steering gear and a steering gear box with a Pitman arm. The vast majority of modern vehicles use a rack and pinion steering gear. A steering gear box with a Pitman arm is still used on some trucks and other heavier vehicles.
There are three basic types of steering linkages used in passenger vehicles and light trucks. These include the rack and pinion linkage, parallel linkage, and Haltenberg steering linkage. There are variations of these linkages, but these are the three fundamental types. The parallel and Haltenburg linkages are used with a steering gear box. The rack and pinion linkage is used with a rack and pinion steering gear.
The steering linkage, depending on which steering gear is used, may consist of the following components; outer tie-rod end, inner tie-rod end, tie-rod, steering knuckle/arm, pitman arm, center link, drag link, idler arm, and steering damper or stabilizer.
The rack and pinion linkage, which is by far the most common steering linkage, consists of inner and outer tie-rod ends on each side and steering knuckles or arms. Advantages of this linkage include precise steering geometry, simple design, and relatively low weight and cost. Disadvantages include relatively low carrying capacity and inflexibility when it comes to fitting around other vehicle components.
The parallel linkage consists of a pitman arm, idler arm, center link, tie-rods, tie-rod ends, steering knuckles or arms, and possibly a steering stabilizer. Advantages of this linkage include precise geometry, high strength, and it can be designed to fit around other vehicle components. The main disadvantages are cost, relatively higher weight, and more components to wear out.
The Haltenberg linkage consists of a pitman arm, drag link, tie-rods, outer tie-rod ends, steering knuckles or arms, and possibly a steering stabilizer. Advantages of this linkage include very high strength, lower cost than parallel linkage, and can be designed to fit around other vehicle components. The main disadvantage is the steering geometry is not precise.
Steering linkage components can be either wear or non-wear components. If the component has a ball joint socket, it is considered a wear component. If the component does not have a ball joint socket but has a bore for the ball joint stud of another component to fit into, it is considered a non-wear component.
Typical wear components include the pitman arm, idler arm, inner tie-rod ends, and outer tie-rod ends. These components use a socket arrangement similar to a ball joint that allows the linkage to move side to side and up and down freely so steering effort does not interfere with the vehicle’s suspension up-and-down motion as the wheels move over the road.
The ball joint socket used in steering linkage components may be either grease-able or lubed for life. Lubed-for-life joints are the most common type. However, it is important to note the life of a part is not necessarily the life of the vehicle. Without regular maintenance, the grease-able ball joint could fail more quickly than a lubed for life joint. In a way, the lubed for life joint was designed for those who are negligent of regular maintenance.
A steering stabilizer may be found on some steering linkages. The steering stabilizer is similar to a shock absorber. The component is connected from one of the steering linkage components to the chassis or frame of the vehicle. The steering stabilizer helps absorb road shock and prevents it from reaching the steering wheel.
The steering linkage is adjustable to be able to vary the toe setting and perform an alignment on the vehicle. This is necessary to account for tolerance stack-ups in frame and suspension components, component wear, and impact damage such as potholes. Did you know the force from hitting a pothole can exceed several tons? This can damage the steering linkage and change the toe setting instantly. The toe setting affects vehicle handling, tire wear, and fuel economy.
Steering linkage components should be inspected for looseness, torn or deteriorated grease seal boots, and other damage. The steering linkage is the most critical part of the steering system because a worn linkage can not only cause excessive tire wear, it can also become a serious safety and liability issue. For this reason, it is important to have the entire steering linkage inspected at least annually by an ASE certified technician.