Control Arm Location: A Practical Guide for Suspension Pros

Knowing your way around a vehicle’s suspension is key for any pro. But for a component as critical as the control arm, where exactly is it located and why the control arm location so important?

A control arm is a vital suspension link located between the vehicle’s chassis and the wheel hub or steering knuckle. Its precise location dictates how the wheel moves, making it fundamental to a vehicle’s handling, stability, and ride comfort.

As specialist manufacturers of automotive parts, including a comprehensive range of control arms since 1998, we at GSW Autoparts understand that these components are the foundation of a vehicle’s handling dynamics. They aren’t just simple brackets; they are precisely engineered linkages that manage immense forces while controlling wheel movement with accuracy. This guide will provide a practical overview of where control arms are located, the different types, and why their positioning is so critical to performance.

Where is a control arm located?

Before we can discuss types, we need to know where to find them. Where are these essential components situated on a vehicle?

Control arms are located in the vehicle’s undercarriage, forming the primary connection between the car’s frame or subframe and the steering knuckle at each wheel. They are a core component of all independent suspension systems, both front and rear.

You won’t see control arms by simply looking at the side of a car; they are tucked away behind the wheels, forming the crucial architecture of the suspension. Think of them as the "levers" that allow the wheel to move up and down to absorb bumps while holding it securely in its correct position. At GSW Autoparts, we manufacture these links for both front and rear independent suspension systems. In a front suspension, they are responsible for allowing the wheel to both move vertically and pivot for steering. In an independent rear suspension, they allow each rear wheel to react to bumps on its own, improving ride quality and stability. They are the fundamental reason your wheels can move independently of the car’s body, which is the very definition of a modern suspension system.

What Is a Lower Control Arm Location?

The lower control arm is the most common type of control arm. Where is its specific location and what is its primary role?

The lower control arm is located beneath the centreline of the wheel axle, connecting the bottom of the steering knuckle or hub carrier to a low mounting point on the vehicle’s chassis or subframe.

The lower control arm is a fundamental component found in virtually all modern independent front suspension setups, including the extremely common MacPherson strut system used in many popular UK cars like the Ford Fiesta or Vauxhall Corsa. In this setup, the lower control arm forms the bottom side of a triangle, with the strut itself forming another side and the vehicle’s chassis as the third. Its location at the bottom means it often bears the majority of the cornering and braking forces. The vehicle’s coil spring frequently sits on, or acts upon, the lower control arm, meaning it also carries a significant portion of the vehicle’s static weight. Because of the heavy loads it endures, from our manufacturing experience at GSW Autoparts, the lower control arm is typically a very robust, strong component, often appearing larger or beefier than an upper control arm if one is present.

What Is an Upper Control Arm Location?

If there’s a lower arm, there must be an upper arm, right? Not always. So, where do you find an upper control arm?

An upper control arm is located above the wheel’s centreline, connecting the top of the steering knuckle to a higher mounting point on the vehicle’s frame or shock tower. It is found in more advanced suspension designs like the double wishbone system.

You won’t find an upper control arm on every car. It’s a key feature of more performance-oriented suspension designs, most famously the double wishbone suspension (also called an SLA, or Short-Long Arm system). This design is often used in sports cars, performance saloons, and many trucks and SUVs where handling precision is a priority. Located above the wheel hub, the upper control arm works in tandem with the lower arm to create two distinct pivot points for the steering knuckle. This "wishbone" setup gives engineers much more precise control over the wheel’s movement, particularly the camber angle (the inward or outward tilt of the tyre). By carefully designing the locations and lengths of the upper and lower arms, engineers can ensure the tyre remains flatter on the road during hard cornering, maximising grip and stability. As a supplier of parts for a wide range of vehicles, we at GSW Autoparts produce both the common lower control arms and the more specialised upper control arms for these performance applications.

Why Control Arm Location Matters?

Why is the precise mounting point of a control arm so important? It’s because their location and geometry dictate the entire handling personality of a vehicle.

Control arm location is critical because it defines the suspension’s geometry, directly influencing key handling characteristics like camber, caster, and steering feel. Even a small change in location due to damage or wear can ruin a car’s stability and tyre life.

From a manufacturer’s perspective, the location of the control arm pivot points is one of the most fundamental aspects of chassis design. This is not just about connecting point A to point B; it’s about physics.

• Camber Control: In a double wishbone system, making the upper control arm shorter than the lower one creates what’s called a "camber gain¹." As the car rolls in a corner and the suspension compresses, the top of the wheel is pulled inwards, keeping the tyre’s contact patch flatter on the road for more grip. The precise location of the arms dictates how much this happens.
• Caster and Stability: The fore-and-aft position of the control arm mounts on the chassis determines the caster angle² of the steering axis. Proper caster is what gives a vehicle high-speed stability and helps the steering wheel return to centre after a turn.
• Scrub Radius: The geometry created by the control arms and ball joints also defines the scrub radius³—the distance between the steering axis pivot point and the centre of the tyre contact patch. This affects steering effort and how the car reacts to bumps or braking on split-friction surfaces.

This is why a bent control arm from hitting a pothole is so serious. It completely alters this carefully engineered geometry, leading to poor handling and rapid tyre wear. It’s also why our GSW replacement arms must be manufactured to exact OEM specifications to restore proper vehicle dynamics.

Is a control arm the same as a suspension arm?

You often hear different terms used for suspension links. Are "control arm" and "suspension arm" just two names for the same thing?

Yes, generally, "control arm" and "suspension arm" are used interchangeably to describe the same type of component. "Suspension arm" is a broader, more generic term, while "control arm" is a more specific and widely used technical name.

In my 25+ years in the automotive parts industry, I’ve found that terminology can sometimes be confusing. Here’s a simple breakdown:

• Suspension Arm: This is a very general term for almost any linkage in a suspension system that connects the wheel assembly to the chassis. It’s a perfectly correct, though less specific, description.
• Control Arm: This is the more common and specific name for the primary suspension arms that control the wheel’s position and movement, especially those that are A-shaped or L-shaped.
• Wishbone: This term is often used as a synonym for an A-shaped control arm, because it looks like a chicken’s wishbone. A double wishbone suspension⁴, therefore, uses two A-shaped arms.
• Link: In a modern multi-link suspension⁵, you might find five or more individual arms connecting to the wheel hub. Each is technically a "suspension arm," but they are often referred to as individual "links" (e.g., camber link, toe link, trailing link) because each one has a specific job in controlling one aspect of the wheel’s movement.

So, while you can call a control arm a suspension arm, "control arm" is the more precise term you’ll hear used by mechanics and in service manuals. At GSW Autoparts, we manufacture a whole range of these, whatever you choose to call them!

Conclusion

The location of a car’s control arms, whether upper or lower, is fundamental to its design. These critical links form the bridge between your car and the road, dictating safety, comfort, and handling.