everything you need to know about extended balljoints, including how to install them

I’m sure many of you are here because you want to learn a bit more about the black art of suspension geometry. More specifically, roll center, and whether you really need to install extended ball joints or roll center adjusters on your car. I’ll try my best to explain it as simply as possible and help you better understand how impactful these extended ball joints can be on your car’s handling characteristics.

Do you need these for your car? The short answer is yes, if you don’t need any more reason than that, just go order yourself some right now. But if you want to learn about the science of why this will help your car so much, please continue reading…

Roll center is a definitive point of reference in vehicle dynamics, serving as the axis around which a car’s chassis pivots when subjected to lateral forces during cornering. It is ingeniously crafted through the suspension design, with distinct roll centers for both the front and rear suspensions, catering to the uniqueness of their operations. The roll center is undoubtedly the linchpin of a vehicle’s handling characteristics. It commands immediate influence over the car’s balance and stability, unlike anti-roll bars, shocks, and springs that necessitate actual body roll to take effect. Savvy drivers and engineers leverage the adjustment of the roll center as a potent tool to elevate the car’s handling prowess, tapping into an aspect that, though often overlooked, is paramount for optimal vehicle performance.

Determining your car’s roll center is a straightforward process, beginning with pinpointing the “Instantaneous Center.” This crucial point is where the upper and lower wishbone or arm axis intersect or, in the case of a Macpherson strut setup, where the lower wishbone meets a plane that rests perpendicular to the strut axis. The Instant Centers are essential not only for locating the roll center but also for optimizing the steering geometry. This fine-tuning can eradicate the issues of bump steer and minimize roll center movement, ensuring your car handles with precision. It’s important to remember that all measurements should be taken with the car set at its normal ride height for accuracy.

The image provided is a clear visual aid to grasp a concept that might have seemed elusive before. You’ve pinpointed the Instant Center, marked by the bold dark red dots.

Next, engage in a bit of theoretical drawing: extend a line from the center of the tire (the contact patch) directly to the Instant Center (those dark red dots). Draw a line from the right tire’s center to the left Instant Center, and another from the left tire’s center to the right Instant Center. The intersection of these lines reveals your Roll Center, highlighted by the striking bright red dot.

It’s highly unlikely you’ll find yourself doing these measurements. Why would you? The legwork has been efficiently handled by aftermarket companies, who have engineered their products to perfectly align with your needs. Consider this explanation a way to demystify what a Roll Center is, bestowing you with knowledge that, while practically unnecessary for you to measure, enhances your understanding of vehicle dynamics.

Understanding the roll center is crucial to grasp how it influences your vehicle’s handling. Now, let’s delve into the concept of your car’s center of gravity (CG). While pinpointing your car’s exact CG can be complex, for our purposes, it’s not necessary to dive into that level of detail. You can easily find the formula with a quick Google search, or simply consider the crankshaft of the engine as a general approximation of the CG’s location.

This is particularly relevant for enthusiasts such as ourselves, as a comprehensive understanding of the CG is not imperative. However, it’s vital to discuss the CG in the context of explaining roll center’s impact on handling. Typically, your CG will be situated above the roll center. With the location of both the roll center and the assumed CG in mind, drawing a vertical line between them will define your “roll moment arm.”

The roll moment arm functions akin to a fulcrum in a lever system when your car navigates turns. The length of this arm significantly influences the vehicle’s tendency to roll. A longer roll moment arm translates to greater ease for the car to lean into turns—this isn’t about flipping over but rather how the car ‘rolls’ at corners. Essentially, a lever affected by centrifugal force that encourages the car to tilt. A longer lever (which corresponds to a lower roll center) facilitates this rolling motion, whereas a shorter lever (associated with a higher roll center) makes the car more resistant to such leaning dynamics. Understanding this mechanic allows you to tweak your car for optimal performance in turns.

Here’s the hard truth that might just redefine the way you think about lowering your car: When you examine the mechanics closely, the connecting line between the roll center dot and the CG dot on the “stock suspension” is indeed shorter than the one on the “lowered suspension.” This line, known as the Roll Momentum Arm, operates much like a lever—the greater the distance between the two points, the more leverage is created and the easier it is for the body to roll.

Now, your intuition might be telling you something is off. It’s bewildering, I know. You lower your vehicle expecting sharper handling, yet on paper, it seems like you’ve just sabotaged the suspension’s geometry. But here’s the clincher: it’s all about the upgrades. By lowering your car, you’ve likely installed stiffer springs and superior shocks, not to mention you’ve reduced the car’s center of gravity. These enhancements overcompensate for the apparent “worsened” geometry, making your car feel more nimble and responsive.

So yes, while it’s true that lowering has shifted the roll center unfavorably—creating potential issues like bump steer and other unwelcome suspension quirks—the overall improvements to the suspension components and the lower center of gravity provide that convincing illusion of improved handling. Just remember, it’s not always what meets the eye; the devil is in the details of your car’s upgraded components.

Imagine achieving automotive perfection by aligning the roll center of a vehicle precisely level with its center of gravity. In this engineering marvel, as the car corners, body roll would be utterly nonexistent, vanquished by the absence of a lever for centrifugal force to exploit. This precise calibration effectively neutralizes the roll moment arm—the crucial distance between the roll center and the center of gravity—transforming the driving experience.

Do keep in mind, though, that such an extreme alignment, while reducing body roll, might introduce other challenges. However, this concept crucially illuminates just how pivotal a short roll moment arm is to vehicle dynamics.

Consider that with every modification lowering a car, you’re inadvertently expanding the roll moment arm’s reach. It’s simple physics: envision the roll moment arm as a lever coaxing the car to tilt when negotiating a bend. A lengthier lever magnifies the roll. Both elevating the center of gravity and dipping the roll center extend this imaginary lever.

Even when lowering the vehicle lowers both the roll center and the center of gravity, the truth is that the roll center drops disproportionately, elongating the roll moment arm—and that’s precisely why the issue of body roll becomes particularly prominent in lowered cars.

* When the RC is far away from CG (lower RC), when the car corners the CG has more leverage on the RC, so the car will roll more.

* When the RC is closer to CG (higher RC), when the car corners the CG has less leverage on the RC, so the car will roll less.

Optimizing your roll center is a key upgrade for any performance enthusiast. By leveling out your suspension arms, you’re directly tapping into the full potential of the vehicle’s engineering. This adjustment ensures your CV (constant velocity) joints operate smoothly, minimizing wear and preventing binding. Moreover, it enables your suspension geometry to function within its optimal range, thereby maximizing efficacy. Such tuning also extends your shock travel, ensuring that shocks absorb impacts effectively rather than bottoming out on larger bumps. If you’re aiming for both peak performance and longevity in your vehicle, then aligning the roll center is a strategic move you cannot afford to overlook.

Effects of Front Roll Center Adjustment: Front roll center has the most effect on on-throttle steering during mid-corner and corner exit.

LOWER front roll center
* More on-throttle steering
* Car is less responsive
* Better on smooth, high grip tracks with long fast corners

HIGHER front roll center
* Less on-throttle steering
* Car is more responsive
* Use in high grip conditions to avoid traction rolling
* Use on tracks with quick direction changes (chicanes)

Effects of Rear Roll Center Adjustment: Rear roll center affects on- and off-throttle situations in all cornering stages (entry, mid, exit)

LOWER rear roll center
* More on-throttle grip
* Less grip under braking
* Use to avoid traction rolling at corner entry (increases rear grip)
* Use under low traction conditions
* Increases traction, reduces rear tire wear

HIGHER rear roll center
* Less on-throttle steering
* Car is more responsive
* Use in high grip conditions to avoid traction rolling
* Use on tracks with quick direction changes (chicanes)

Roll center dynamics are pivotal in vehicle handling, and this guide is designed to give you a definitive understanding of how they impact performance. Recognize that there are myriad strategies for setting up a vehicle, but the focus here is to elucidate the concept of roll center and its influence on your car. The critical takeaway is the value of extended ball joints as an exceptional modification for enhanced handling dynamics. While moderation is key — as overextending adjustments can yield negative results — rest assured that manufacturers of these components have invested in extensive research and development, ensuring you get the ideal balance without the need for personal trial and error.

In essence, the concept of Roll Center is a critical element in the fine-tuning of a vehicle’s suspension. Elevating the roll center confidently translates to a vehicle with superior resistance to rolling over. This strategic adjustment realigns the suspension to function within its ideal performance boundary. Moreover, it enables the incorporation of softer springs and sway bars, effectively negating the need for stiffer components that traditionally counteract excessive body roll. Additionally, a heightened roll center plays a pivotal role in mitigating bump steer, ensuring a smoother and more controlled ride.

Let me talk about my personal firsthand experience that I immediately noticed after I installed these.

• Car turned in easier, and with less steering input.
• when switching lanes and going over the dots in the road there wasn’t as much feed back in the steering wheel.
• less understeer.
• since there is less body roll I found myself going much faster through corners than before. because the car isn’t rolling as much so it doesn’t seem like im traveling that fast through a turn
• under hard braking the car was less unstable.

Now mind you, when I’m talking about going faster through corners, I’m talking about corners where I felt the car was at the limit at 80-90 mph; I can now take them at 100 mph and have it not even feel near the limit. I would probably have to go 110-120 mph before my butthole would pucker. When I talk about hard braking, I’m talking about braking from 80 down to 20 as late as possible to enter or exit freeways. The car just feels so much better, but it’s hard to put fully into words, and trust me when I say, everyone should do this to their car. Even if it’s not that low, even if you don’t want to track your car, this will just improve the overall driving experience. It will go over bumps and uneven surfaces smoother than before; it will allow you to soften the dampening on your shocks, run softer sway bars or springs, which again will improve the overall ride quality. When I posted that I was installing these on my Instagram, someone commented that this mod was “one of the most slept on mods for double wishbone cars,” and I couldn’t agree more. When I look back at how long I have been driving lowered Hondas or just lowered cars in general—20 years now—I’m mad at myself for never wanting to install extended ball joints/roll center adjusters. I have been driving around with stock ball joints forever, thinking that it couldn’t get any better, but I was wrong! Do yourself a favor and order yourself a pair; it doesn’t have to be the Buddy Club ones like I got. It can be any brand; they will all raise the roll center.

OK, now that you want to order some, let me show you how easy it is to actually install them. (I never did these for fear of how difficult I thought it would be to install them), so if you’re anything like me and you hesitate to do this modification because you are scared that it might be too difficult, trust me, it’s super easy!

Step 1:

Break the lugs loose, jack the car up, place on jack stands, and remove the front wheels.

Step 2:

You’re going to completely remove the spindle off the car so you can easily remove/install the ball joint.

Start by removing the 32mm axle nut

then remove the brake caliper, and rotor.

Above are the holes where the brake caliper bolts to the spindle.

Now remove the lower ball joint, the upper ball joint, and the tie rod end

Use a hammer to smack against the spindle to “shock” the ball joints and tie rod loose. As you can see, I flip the castle nut upside down and thread it back on to help protect the threads from damage when swinging the hammer. Don’t be afraid to hit very hard many times until they come loose.

Once you get the upper and lower ball joint loose, the spindle will come out. Just slide the axle out of the hub carefully, not pulling too hard on it, or the axle might come out of the transmission, which will cause some of your fluid to leak out.

You should be left with a wheel well that looks like this. Notice that everything can still stay connected; you just take everything off the spindle.

Step 3:

Removing the old ball joint. Locate the Circlip

Now take Circlip pliers and remove it.

Now the ball joint is ready to be removed. Simply position the spindle like so, and hit the ball joint hard a few times with a hammer and it will just fall right out.

As you can see, there is a difference in the ball joint lengths. This is what raises the roll center. One thing to take note of is that the extended ball joint will place the lower arm closer to the brake rotor, and you might have to remove the brake dust shield, so it doesn’t get pushed into the brake rotor when the suspension is at ride height, or under compression while cornering. It’s pretty close; I don’t have a dust shield, and there is still only about 0.5 inch of clearance. It is kind of scary, but I haven’t had any issues with brake rotor to lower arm contact, and neither has anyone else that I know who runs these.

Step 4: 

Installing the new ball joint. Make sure to thoroughly clean all debris out of the spindle where the ball joint gets pressed into, and I lubed it with some grease to aid in proper seating. You will also have to use a ball joint press tool; I just went to AutoZone and rented one.

This is what it looks like in action

The new ball joint should slide in easily; you shouldn’t have to use much torque when tightening the clamp. Once the ball joint is fully seated, you will now install the NEW Circlip that came with the ball joints. Make sure you install the Circlip, or eventually, the ball joint will just press back out of the spindle, and you will most likely crash.

Be careful when installing the Circlip that it doesn’t come off the pliers and snap on the boot, possibly causing damage to the boot, and for sure you’re going to mess up the stickers like I did too.

Step 5:

Reinstall the spindle on the car. It should just go right back on the same way you took it off.

1. As you place the spindle back in, line up the axle and slide it through (spray some WD-40 or some other lubricant to help the splines slide into the hub easier),
2. once all the balljoints are in you won’t be able to slide the axle in.
3. Re install the upper and lower ball joints, and the tie rod and tighten completely.
4. Then install the suspension fork onto the shock and lower arm, but don’t fully tighten.
5. Put the brake rotor back on, then the brake caliper, and the brake line bracket and tighten it all completely.
6. Tighten the axle nut and take a punch to lock it in place in the notch at the end of the axle.
7. Now take a jack and place it under the lower arm, put some tension on the suspension so that the fork properly seats tight against the bottom of the shock, and tighten the bolt clamping it to the shock, and on the lower arm.
8. Lastly double check that you have tightened everything that you had originally loosened.

You will repeat the same removal/install process for the opposite side and once both sides are done, reinstall the wheels and lower the car back down.

Since installing these is going to raise your roll center, it’s going to lower your car more, so you will most likely want to jack the car back up and adjust your ride height. As you can see below in my before and after photos, it will be about an inch lower.

Before:

After:

You are definitely going to need to get an alignment again because the toe will be off. I have previously covered how to do your own garage string alignment if you’re feeling confident and want to try something that is actually pretty easy. If not, just make sure you get an alignment before doing any hard driving.

Here’s the link on how to do your own alignment.

PSA about hardrace super tie rods/DIY string alignment

See more

Hopefully, this article helps you understand why roll center adjusters are such a worthwhile modification. I also hope that the way I explained it was easy enough for you all to understand. As always, thanks for reading, and I hope this article can help inspire you to do some work on your own car this weekend. If you like what you’re reading, please feel free to share, like, or comment. Or if you have any questions, please don’t hesitate to ask.