The device of any modern car includes such a part as a steering knuckle. It is difficult for some to attribute it to a particular car system, since the part performs some functions of several mechanisms.
Let us consider in more detail what is the feature of the element, we will talk about the types of parts, as well as the principle of replacing it when such a need arises.
What is a steering knuckle
We can safely say that a fist is a multifunctional detail. It is installed at the junction of several systems, which is why there is a difficulty with classification: to which specific system this element belongs.
It holds the steering part, wheel hub, shock absorber strut and other equipment (for example, brake elements). For this reason, the fist is the node on which the system data is connected and synchronized. Since there are serious loads on this part, it is made of durable material.
Some manufacturers use high alloy steel for their products, while others use cast iron. Another feature of the steering knuckle is its extremely precise geometric shape. The shape of the knuckle can be very different depending on the type of suspension and steering.
What is a steering knuckle for?
The name itself implies one of the purposes of installing this part in the car - to ensure the rotation of the front wheels. If the car is rear-wheel drive, then the fist will have a simpler device.
It is much more difficult to ensure the rotation of the drive wheel, since in addition to changing the trajectory, torque from the transmission must be applied to its hub. The presence of a steering knuckle solved several problems at once:
- Provided stable fixation of the rotating hub, on which the drive wheel is fixed;
- It made it possible to connect the rotating wheel not only to the transmission, but also to the suspension. For example, in the McPherson modification (its device was discussed a little earlier) the shock absorber strut of many cars is mounted on this particular part;
- Allows the unit to turn without losing power as the wheel spins and suspension contractions while riding.
Thanks to such functions, the fist is considered both a support in the chassis and an actuator for the steering of a car. In addition to the listed functions, some parts of the braking system are attached to the knuckle.
If a part is made with geometric errors, some systems can quickly fail.
The spare part in question is used on the front axle. Sometimes identically referred to as the rear wheel hub support. They have a similar design, only in the second case, the part does not provide the ability to rotate, so it cannot be called rotary.
To make the suspension work with the fist, holes are made in the fist for attaching the lever (at the bottom) and the shock absorber (top). The stand is attached with a conventional bolt connection, but the lever is through a ball joint. This element allows the wheels to turn.
The steering system (namely the tie rod) will also be attached with ball pieces (called tie rod ends).
To ensure the rotation of the steering wheels, a bearing (rear-wheel drive car) or CV joint (front-wheel drive car) is inserted into the steering knuckle.
Depending on the conditions on the road, the steering knuckle can simultaneously provide wheel rotation, its damping, and the supply of torque to the drive hubs.
For how all the systems in a node interact, see the following video based on an overview of the car's suspension:
Device and varieties
Manufacturers use different suspension systems in their cars, so the shape of the steering knuckles also varies. This is the very first reason why you should select a part in accordance with the car make. The VIN code will help in the search, which indicates the features of a particular car (on how to decipher all the characters, read separate article).
Even the slightest discrepancy can either make it difficult to install the part, or the operability of the mechanisms. For example, due to improper fastening, the tie rod will not be able to turn the wheel to the end, because the ball has become at the wrong angle, etc.
It is on the steering knuckle that additional equipment is attached, for example, brake calipers, as well as sensors.
It would be a mistake to think that the manufacturer uses the same design of these parts in all cars in the model range. For example, when a manufacturer initiates a restyling procedure (about what it is and why automakers do it, read here), engineers can change the design of the part so that it is possible to mount a sensor on it, which was not in the pre-styled version.
Malfunctions and possible symptoms
There are several symptoms by which the driver can determine that there is a problem with the steering knuckle. Here are some signs:
- When driving in a straight line, the vehicle is pulled to the side. In this case, the alignment is checked first of all (how the procedure is done, read in another review). If the problem persists, the problem may be in the fist;
- The steering angle of the wheels has decreased markedly. In this case, it is worth checking the ball joint first;
- The wheel came off. Most often this happens due to the failure of the ball (the finger was cut off), but this often happens when the eyelet for mounting the mount breaks;
- Cracked housing or worn bearing mounting location. This sometimes happens with an illiterate installation of the chassis elements (the bearing is crookedly pressed in or the bolts on the wheel are not fully tightened).
As for the formation of cracks, some car mechanics offer to restore the part - to weld it. If the spare part is steel, then it must be restored. Most of the kulaks are made of cast iron.
Even if the welder manages to hide the crack, the material itself loses its properties at the processing site. The part that is being welded will quickly break down at the first serious hole.
For safety reasons, if any defects are found, it is better to replace the part with a new one. How this is done, see the example of a specific car:
How to remove the steering knuckle?
In order to be able to remove the steering knuckle, you will have to disconnect all the elements that are attached to it. The procedure is performed in the following sequence:
- The machine is put on a jack or hung out on a lift;
- We unscrew the corresponding wheel;
- Dismantle the brake caliper;
- Unscrew the shock absorber strut mount;
- We press out the tip of the tie rod. In order not to have to change it, it would be better to arm yourself with a special tool;
- Dismantle the axle shaft from the hub;
- We unscrew the sensors and other equipment, if any in the car. In this case, it would be better to remember where what is attached. To do this, just take a photo on your phone
- Dismantle the fist itself. To do this, use a flat screwdriver to disconnect the fastening of the retaining ring on the ball joint installed on the lower arm;
- The last step is to remove the hub from the fist (the lock nut is unscrewed), before that the splines are unclenched. Next, the wheel bolts are screwed in, and the hub is knocked out from the back side with light blows.
Before unscrewing bolts and nuts, it is important to adhere to a simple principle: in order to reduce the impact on the edges of the retainers, they are cleaned of dirt and rust, and then treated with a penetrating liquid (for example, WD-40).
Steering knuckle cost
Manufacturers make steering knuckles with a decent margin of safety. Consequently, the part breaks only under excessive loads, and natural wear occurs slowly.
In some cases, parts are changed as a kit. As for the steering knuckles, this is not necessary. The cost of this element is from $ 40 to more than $ 500. This range of prices is due to the characteristics of the car model and the manufacturer's pricing policy.
In this case, the quality of the part often matches the price. For this reason, it is better to give preference to a well-known manufacturer, even if its products are not included in the category of budget goods.