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What do upper and lower control arms do?
The functions of the components may vary insignificantly depending on the suspension design. For instance, in double wishbone suspensions the upper control arms hold the upper part of the steering knuckle, which prevents the wheel from tilting during driving. The lower ones also hold the knuckle and at the same time hold the lower end of the shock absorber to prevent it from rocking. In a multi-link suspension, the upper control arms transmit lateral forces and connect the knuckle with the subframe. The front lower arm determines the wheel toe-in. The rear lower arm takes the weight of the car body through the spring.
What are the signs of a faulty control arm?
In case of control arm failure, the vehicle may pull to one side. The wheels become misaligned. The tyres wear unevenly. The shock-absorbing properties of the suspension are impaired, which is especially noticeable when driving on poor quality roads. While driving, you can hear distinctive sounds: knocking, squeaking, or clicking. As a rule, this occurs on rough roads. On a smooth surface, specific humming can be heard from the suspension, and screeching when steering. Oversteer or understeer can occur and there may be steering delay.
Is it dangerous to drive with a bad control arm?
A faulty arm causes poor handling, which negatively affects road safety. There is a high risk of skidding on slippery surfaces. A broken control arm poses a risk of excessive tilt of the wheel, which is very dangerous when driving at high speed, because you could lose control of the car completely.
How do control arms go bad?
The most vulnerable elements of these components are bushes and ball joints. The former harden and crack over time, their rubber part can detach from the metal one. As for the ball joints, their insert and ball wear out, which results in free play. If replacement is not performed in due time, the fasteners and mounting seats of the bushes and ball joints can break down due to higher loads and free play. This increases the risk of control arm breakage when the wheel runs over an obstacle. Take into account that even a new part may break down due to a severe impact. In some cases, the strength of the components reduces due to corrosion.
Can I only replace one control arm?
You could change only the damaged control arm, but it’s recommended to replace these parts in pairs especially if they have been used for a long time. Even a control arm used for a short time may have different technical characteristics from those of the new component. In addition, the parts have approximately the same lifespan. Therefore, the failure of one usually means the other will break down soon.
How long does it take to replace control arms?
Replacement of these components may take 1–5 hours. The process of removing and installing the parts is rather labour-consuming. The tools you will need include a lifting jack and spring compressors. Also, the job usually involves removing the brake mechanisms. After mounting new control arms, independently of whether they are upper or lower, it is mandatory to have the wheels aligned. It is important to perform this procedure properly, as its correctness is highly important for a long service life of tyres and other suspension elements, vehicle steerability, and road safety.