Control Arms

A control arm is the hinged link between the chassis and the hub carrying your wheel. It pivots on bushes at the chassis end, connects to the hub through a ball joint at the other, and its job is to let the wheel travel up and down while holding it exactly where the alignment says it should be.

Because the arm is a lever, whatever movement it allows at the pivot is multiplied by the time it reaches the tyre. That is why control arms have more influence over how a car drives than almost anything else bolted to it.

Upper, Lower and What Each One Holds

Which arms your car has depends on the layout the manufacturer chose.

A strut suspension typically uses a single lower control arm per side, with the strut locating the top of the hub, so the front lower control arm does all the work of positioning the wheel and carries the lower ball joint. Double wishbone suspension uses upper and lower control arms together, which gives finer control over how camber changes through travel and is why it turns up on performance cars, trucks and solid front axle designs.

You will hear the same part called a wishbone or an A-arm depending on its shape and who is talking. They mean the same thing.

At the rear, control arms turn up as lateral links, camber arms, toe arms and trailing arms depending on what each one is holding. Position and shape matter more than the name when you are ordering.

Control Arm Bushes or the Whole Arm

This is the question worth answering before you spend anything, because the cheaper option is often the right one.

Control arm bushes are the wear item. Factory rubber is chosen for quietness rather than control, and it deflects under load even when new, then perishes, cracks and compresses as it ages. Fresh polyurethane front control arm bushes or rear bushes remove that deflection and stop the geometry wandering while you drive, which is usually the difference people actually feel.

Replace the bushes alone when the arm is straight, the mounting eyes are round, the ball joint is still tight and the ride height has not changed. That covers most older cars and it is the cheapest route by a wide margin.

Buy the complete arm instead when the ride height has changed and you need correction the factory never built in, when the arm is bent or corroded, when a mounting eye has worn oval and will no longer hold a bush, or when the ball joint is pressed into the arm and has failed.

Worth knowing that the arm has to come off the vehicle for either job, so the labour is identical. Once more than one thing on an arm is due, a complete assembly frequently works out better value than a rebuild, and control arm bushing replacement cost is mostly labour rather than parts.

When Factory Arms Run Out of Adjustment

Manufacturers build in just enough adjustment to correct production tolerances and not a millimetre more, which is fine on a standard car at standard height.

Lower the car and the arms swing through a different part of their arc. Camber goes negative, toe follows it, and on plenty of platforms the car ends up outside specification with nothing worn at all. Raise it and the same thing happens in the opposite direction, with caster washing off as the geometry rotates.

At that point the alignment shop has nothing left to work with. The numbers are out of range, and something has to physically move a mounting point before the machine can do anything about it.

That is what corrected and adjustable arms are for. They are not a luxury on a modified car, they are what makes the alignment achievable.

Adjustable and Fixed Offset

Adjustable control arms let the length be set, which hands the aligner range that did not previously exist. Because each side adjusts independently, they also fix problems a symmetrical correction cannot, like a car that has settled unevenly or pulls to one side with tyres and pressures ruled out. Adjustable upper control arms are the usual answer on a raised vehicle where caster and camber both need recovering.

Fixed offset arms have the correction designed into the shape of the arm instead. They are right the moment they are bolted in, nothing can move or work loose, and on a vehicle sitting at a known ride height that reliability is often worth more than adjustability.

On a raised 4WD or ute there is a second reason to look at upper control arms beyond the alignment. A factory upper ball joint is built around factory travel, so once the vehicle is lifted the arm works at a steeper angle and the joint articulates further than it was designed to at full droop. It binds, tears its boot, and wears out early, which is why people fit a lift and then start replacing upper ball joints regularly.

Signs Your Control Arms Need Attention

• A dull clunk or thud from the front over bumps, driveways and speed humps
• Clunking that appears when the wheel is turned and loaded, which points at the ball joint
• Steering that feels vague or wanders and needs constant correction
• The car pulling to one side under braking
• Shudder or vibration through the wheel when braking from speed
• Uneven tyre wear, usually across one edge
• An alignment that will not hold spec between services, or one the shop cannot reach at all
• Cracked, split or squeezed out material in the control arm bushes
• A torn ball joint boot, or grease thrown around the inside of the wheel
• Visible bending, cracking or heavy corrosion after a kerb strike or pothole

A bent arm is worth checking for specifically if the car has hit something hard and the alignment has never been right since. A few millimetres of deflection looks like nothing and changes where the wheel sits entirely.

What Replacement Involves

A complete arm bolts into the factory mounting locations and arrives assembled, which is the main reason to buy the arm rather than the pieces.

Support the car properly and take the load off the suspension before separating a ball joint, since a joint under spring load releases suddenly. Use a ball joint separator rather than a hammer.

Where you are pressing bushes instead, use a correct diameter press tool. The mounting eye is the expensive part and improvising with sockets is how arms get ruined.

Fit both sides where the wear is age related, because a new arm working against a tired one leaves the front end with different amounts of compliance left to right.

Torque the inner fasteners with the car on its wheels at ride height rather than hanging at full droop. Whatever position a bush is clamped in becomes its neutral position, so an arm torqued at droop spends its life twisted and binds from the first kilometre. This is the most common mistake on control arm work and it costs nothing to avoid.

Book the wheel alignment for the same visit, since replacing an arm changes camber and toe immediately and the previous settings no longer apply.

Find Control Arms for Your Vehicle

Want sharper turn-in? Browse the rest of our suspension arms range for camber, caster and toe adjustment.

Select your vehicle to see the control arms, arm kits and bush kits available for it, and check each listing for the position and side it suits along with any correction it provides. Every Whiteline component is backed by our warranty, a fitment guarantee and 60 day returns.