Most cars have two control arms in the front suspension. Often they are called lower control arms. Some cars and many trucks have four control arms, two upper and two lower arms.
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| Upper and lower control arms |
A control arm connects the frame or body of a car to the assembly that holds a front wheel. This assembly is called a steering knuckle.
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| Car schematic showing lower control arms |
Control arms are connected to the frame or body of a car through flexible rubber bushings, called control arm bushings. This allows a control arm to swing up and down as front wheels roll over bumps and potholes. The outer end of a control arm has a ball joint. In some cars, a ball joint is bolted to or pressed into the control arm and can be replaced separately. In others, a ball joint comes with a control arm as one piece. Control arms have a very important role holding both front wheels on the road. If a control arm is excessively worn, damaged or bent, the vehicle is NOT SAFE to drive.
Control Arm Problems
There are a few reasons why a control arm may need to be replaced. A worn-out ball joint that cannot be replaced separately is one of the most common reasons. A ball joint is an extremely important component. If it wears out, the car is unsafe to drive: the front wheel can separate from the lower suspension causing the vehicle to lose control. This is very common with but not exclusive to older model Hondas.
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| A separated ball joint |
In the photo above, the ball joint has separated while driving, although the owner was lucky that it happened at a slow speed. If this had happened on the highway, the outcome could have been much worse.
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| A bad control arm bushing |
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| New and old control arm bushings |
The control arm is also the most common part that bends in a collision involving one of the front wheels or after hitting the curb. A bent control arm must be replaced.
How To Check A Control Arm
The only way to inspect control arms and several other suspension components is when the vehicle is lifted (jacked).
Symptoms of a bad control arm bushings or a ball joint include a popping or clunking noise when driving over bumps, or when accelerating and decelerating. In some cases, a car may feel unstable and "wander" during braking or when driving over rough surfaces.
However, the symptoms might not be noticeable at all if its just started going bad. This is one of the reasons why it is important to have your vehicle inspected at least once a year by a skilled mechanic with the vehicle lifted on a hoist or at least lifted by a hydraulic jack safely.
Control Arm Replacement
It's not necessary to replace both, left and right arms if one is bad. However, if one arm is worn out, it's reasonable to expect that another control arm will likely need replacement soon. In this case, it's makes more sense to replace control arms on both sides at the same time.
After control arm replacements, a wheel alignment must be done.
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| Add caption |
Stabilizer bar is usually connected to the lower control arms via stabilizer bar links. Sometimes, a nut that holds the stabilizer bar link could be seized and cannot be removed without damaging the link. In this case, your mechanic might recommend replacing the stabilizer bar links as well. In most cars, the links are not very expensive and doesn't require any extra labour when the control arm is replaced.
Can control arm bushings be replaced separately? In some cases, worn out control arm bushings can be replaced separately. However, control arm bushings need to be pressed in with a special tool or press, which takes some time and adds the labour cost.
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Email; vverteautosevcs@gmail.com
Phone; 09137103730
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