![\"OEM](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/upper-control-arms-1024x576.jpg\")
<\/figure><\/div>\n\n\nControl arms have 2 main responsibilities:<\/p>\n\n\n\n
- \n
- Control, and<\/li>\n\n\n\n
- Isolation.<\/li>\n<\/ol>\n\n\n\n
Simply put, their main goal is to connect the wheels to the frame. They control the steering knuckle’s movement at the front end by confining it to a vertical trajectory. Each arm (upper and lower) has 2 chassis pivots which allow up and down motion but prevent lateral tilting.<\/p>\n\n\n\n
The knuckle or spindle is connected to the control arm via ball joints, consequently controlling the wheels’ side-to-side movement.<\/p>\n\n\n\n
Combine the two, and you get a system that enables the wheels to articulate vertically and move side-to-side as they cycle through compression, extension, and steering.<\/p>\n\n\n\n
Additionally, wheel alignment angles such as camber, caster, and toe are determined partly by the length and angle of your control arms.<\/p>\n\n\n\n
Many 4×4 trucks with solid-axle setups utilize control arms, but they’re far more prevalent in independent suspension systems such as:<\/p>\n\n\n\n
- \n
- Double Wishbone<\/li>\n\n\n\n
- MacPherson Strut<\/li>\n\n\n\n
- Multi-link<\/li>\n\n\n\n
- Semi-trailing arm<\/li>\n<\/ul>\n\n\n\n
Control arms come in many shapes and sizes. They’re either A-shaped, or L-shaped, or they’re simply straight rods with a turnbuckle joint in the center and pivot points on each end \u2014 these are often seen on multi-link setups.<\/p>\n\n\n
\n![\"Types](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/control-arm-types.jpg\")
<\/figure><\/div>\n\n\nThe A and L-shaped ones have a ball joint at the narrow end which attaches to the steering knuckle, allowing it to tilt and pivot from left to right. The knuckle is then bolted to the brake rotor and wheel assembly.<\/p>\n\n\n\n
On the other end, the wider part attaches to the chassis in a way that allows it to move up and down. Upper and lower control arms together facilitate the wheel’s vertical and<\/em> side-to-side movements, which determines the arc through which it travels.<\/p>\n\n\n\n
The upper and lower control arms are abbreviated as UCA and LCA respectively.<\/p>\n\n\n\n
Orientation and Positioning<\/h3>\n\n\n
\n![\"Control](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/double-wishbone-suspension-arms.jpg\")
<\/figure><\/div>\n\n\nMost independent suspension systems have upper and lower control arms on all 4 wheels. But with MacPherson setups, the upper control arms are replaced by the strut itself, which is bolted directly onto the body of the car.<\/p>\n\n\n\n
Rear multi-link setups have more than just two suspension arms on each wheel. They also consist of a trailing or traction arm, and often a toe arm. This suspension type is usually seen only on the rear end of front-engine RWD cars due to limited space in the front.<\/p>\n\n\n\n
Front control arms have the added responsibility of working with steering system components \u2014 tie-rods in particular, which allow the wheels to turn about their axis.<\/p>\n\n\n
\n![\"Control](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/front-control-arms.jpg\")
<\/figure><\/div>\n\n\nThe layout, length, and angle of your control arms also depend on the configuration of your drivetrain (RWD, AWD, or FWD) and differential. This is because they need to accommodate the axles and CV joints or U joints, without disrupting the pinion angle and driveline alignment.<\/p>\n\n\n\n
Regardless of the suspension type, it’s the lower arm that does most of the heavy lifting. When driving over road irregularities, it’s the first component that transfers the wheel’s vertical force to the coil springs and the subframe.<\/p>\n\n\n\n
But when it comes to determining the wheel’s alignment angles, it’s the upper control arm that plays the more dominant role. That’s not to say that LCAs aren’t adjustable; most of them are. Even OE LCAs have some amount of adjustability in the form of eccentric bolts.<\/p>\n\n\n\n
It’s just better to rely on UCAs, camber\/caster plates, toe links, and the tie-rod for alignment settings as much as possible because they’re less vulnerable.<\/p>\n\n\n\n
Why Install Aftermarket Control Arms?<\/h2>\n\n\n
\n![\"Adjustable](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/adjustable-control-arm-links.jpg\")
<\/figure><\/div>\n\n\nIndeed, stock suspension setups on passenger cars and even some sporty cars are geared more toward ride comfort than outright performance.<\/p>\n\n\n\n
Automakers will want to tend to the requirements of a larger audience and their business interests. There are also manufacturing budgets, packaging constraints, and design briefs to worry about.<\/p>\n\n\n\n
Despite all that, the factory suspension systems on most cars are shockingly well-balanced. The engineers know what they’re doing.<\/p>\n\n\n\n
It’s no wonder why some of the fastest cars at open track events don’t wander too far from factory suspension settings and prefer a more neutral setup. This also explains why driving instructors in stock cars can run laps around some improperly tuned cars.<\/p>\n\n\n\n
Emphasis on the word “improperly”, because if you want to retain the benefits of all the engineering that’s gone into your factory suspension, you need to tune it the right way. Adjustable control arms are among the many upgrades that allow you to do that.<\/p>\n\n\n\n
More Adjustability<\/h3>\n\n\n
\n![\"SPC](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/spc-adjustable-arm.jpg\")
<\/figure><\/div>\n\n\nFactory control arms do offer some amount of adjustability, but it’s very limited. In this context, adjustability means being able to change the length and angle of your control arms.<\/p>\n\n\n\n
You need adjustability because the orientation of your control arms affects your suspension and wheel alignment angles such as:<\/p>\n\n\n\n
- \n
- Roll center and roll couple<\/li>\n\n\n\n
- Steering axis inclination<\/li>\n\n\n\n
- Scrub radius<\/li>\n\n\n\n
- Camber<\/li>\n\n\n\n
- Caster<\/li>\n\n\n\n
- Toe<\/li>\n<\/ul>\n\n\n\n
When any of these angles change in a way that doesn’t suit your car’s driving dynamics, it causes a domino effect and throws off your suspension geometry. This affects weight transfer, tire load distribution, and traction.<\/p>\n\n\n
\n![\"High-displacement](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/angled-ball-joint.jpg\")
<\/figure><\/div>\n\n\nYour stock suspension and wheel alignment measurements are set by the manufacturer to suit the factory ride height, tire size, and typical usage scenario. That’s why you need to be careful when making changes that involve:<\/p>\n\n\n\n
- \n
- Changing your ride height by lowering or lifting your vehicle.<\/li>\n\n\n\n
- Changing your wheel track by installing negative or positive offset wheels.<\/li>\n<\/ul>\n\n\n\n
For example, UCAs and LCAs hinge from separate pivot points, which means they don’t follow the same arc throughout the suspension’s stroke.<\/p>\n\n\n\n
This causes the wheels to gain and lose camber as they move up and down as the car experiences turning acceleration, and braking. The same applies when you alter the ride height.<\/p>\n\n\n
\n![\"Camber](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/camber-gain.jpg\")
<\/figure><\/div>\n\n\nWhen you lower or lift your vehicle, you inadvertently change the static and dynamic camber angle of your wheels.<\/p>\n\n\n\n
Here’s another example: if your tie rods and control arms aren’t aligned correctly, your wheels will change their toe angle when going over a bump, better known as bump steer.<\/p>\n\n\n\n
Adjustable control arms allow you to offset these unwanted changes in your suspension geometry by letting you change alignment measurements. That’s why they’re also called camber arms.<\/p>\n\n\n\n
The mechanisms by which the control arms are made adjustable include eccentric bolts, slider plates, and turnbuckle joints. It varies significantly for each car.<\/p>\n\n\n\n
Here are some of the features and advantages of aftermarket control arms:<\/p>\n\n\n\n
- \n
- Roll center correction<\/li>\n\n\n\n
- Drivetrain angle correction<\/li>\n\n\n\n
- Additional down-travel clearance for lifted trucks<\/li>\n\n\n\n
- Avoiding coil clearance issues<\/li>\n\n\n\n
- Better quality ball joints<\/li>\n\n\n\n
- On-the-fly adjustments<\/li>\n\n\n\n
- Offsetting camber gain<\/li>\n\n\n\n
- Better contact patch<\/li>\n\n\n\n
- Pinion angle correction<\/li>\n\n\n\n
- Centering the axle<\/li>\n\n\n\n
- Bump steer correction<\/li>\n\n\n\n
- Ability to fit differently-sized tires<\/li>\n<\/ul>\n\n\n\n
OEM Replacement<\/h3>\n\n\n
![\"Moog](\"https:\/\/suspensionsetups.com\/wp-content\/uploads\/2023\/04\/moog-replacement-control-arm.jpg\")
<\/figure><\/div>\n\n\n