Project VA WRX: Finishing the Suspension With Superpro

by Mike Kojima

We have been putting together the Suspension on Project VA WRX over the last few months with some top quality parts from Tein and Superpro.  We were waiting on the few last brand new pieces from Superpro to finish our suspension setup.  Well they have come in and now is our time to install and evaluate them.

The main parts we were waiting on were Superpro's new adjustable front swaybar and their roll center and bump steer correction kits. We had already installed the front lower control arm bushing and caster, anti dive/kit earlier but did not cover their installation in an article yet. 

These last pieces will enable us to go ahead and tune the suspension for optimal performance for use on the track and street.

The Superpro front sway bar is 26mm in diameter vs the stock 24mm part.  It is also 2 way adjustable.  With the bar in the stiff position it is nearly twice as stiff as the stock bar.
The Superpro bar has two positions of adjustment and locating collars so it won't move back and forth during cornering. The collars are an important feature that many swaybars lack.  Side to side movement is an inconsistent free moment that allows the car to roll without the bars coming into play. The bar ends are forged instead of being welded on tabs which is nice.  The bar is finished with a nice corrosion resistant powdercoat. 
The Superpro bar has urethane bushings that are much harder than the stock rubber parts. Harder bushings mean less deflection in the bushings themselves and a more efficient use of the sway bar's torsional stiffness.  The interior of the bushings has a knurled surface which helps retain grease and reduce stiction.  Both of these factors reduce urethane bushings tendency to squeak in use. Superpro's roll center and bump steer kit has balljoints and tie rods with longer studs. These effectively move the front suspension's outer lower control arm pivot point lower .  This raises the roll center of the front suspension.  This corrects the drop in roll center caused by lowering the car.  When a car is lowered the roll center drops faster than the center of gravity giving the front suspension an increased roll moment.  A longer roll moment means that centrifugal force has a longer moment arm to lean the car over under hard cornering. Also when the lower control arm goes past parallel to the ground, the outside front wheel will lose negative camber under roll which contributes to understeer.   If the outer pivot was dropped while the outer tie rod was left alone, the car would tend to toe in under roll with a front steer car, the opposite of what you typically want. You would start to get an annoying amount of bump steer as well.  So the outer tie rod has to be dropped lower as well as the ball joint. 


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Monday, January 11, 2016 7:16 AM
Since nobody makes roll center adjusters for my car, and the ball joints bolt in, do you think it'd be safe to make a metal plate as a spacer?

What my balljoints look like: http://www.autopartsapi.com/eEuroparts.com/images/parts/lg_4643f54a-7b5f-4b9d-98fd-7b95bb6fff64.jpg
Monday, January 11, 2016 9:51 AM
I think I remember reading that simply spacing the control arm further from the ball joint (which is what I think you're suggesting) won't change the roll center at all because the balljoint pivot hasn't moved. Plus, I can imagine it would increase the moment arm between the control arm and the knuckle, which could lead to higher loads going through that hardware. But I'd be interested to see what Kojima-san says. And would also love SuperPro to make Roll Center stuff for my MCX20 Avalon (which is really just a Toyota Solara in a fancy suit)
Mike Kojima
Mike Kojimalink
Monday, January 11, 2016 11:29 AM
What you can do is use special long shank circle track ball joints from a place like Coleman Racing and modify your control arms to take them. Coleman sells special reamers to get the right taper in your knuckle. You have to take into account that this can decrease static negative camber and increase positive caster depending on how your suspension is. You also have to move your tie rod ends or steering rack or have wicked bumpsteer too.
Monday, January 11, 2016 11:55 AM
Duly noted, thanks!

My car has a factory drop of 2 inches, but they did nothing to correct roll center, and it's still high. I've seen pics of other people getting lower, and even with janky camber bolts, they have positive camber. It looks and probably performs awful.

Tie rod is on the top of the knuckle, so I was going to measure how far it'd move by flipping it to the bottom, and make the ball joint that much longer.
Monday, January 11, 2016 1:29 PM
Simple and effective. I did have a question about the "hexagonal" bushings. You stated that the sides were flattened to introduce "engineered flex" to reduce binding. Is this something we can do at home to existing bushings that are known to bind? I have some 40 year old rubber bushings that I'd like to replace, but using poly bushes in their place are known to bind. The alternative is to use spherical bushings that need to be welded in place at the price of $800+. How do these work? Which axis are they flexing on, or do they flex on multiple axes?
Mike Kojima
Mike Kojimalink
Monday, January 11, 2016 1:42 PM
You kinda need to look at the suspension to determine where you need some freedom of movement and where it helps to be constrained if you are going to mod your bushings. You could drill holes or make some relief grooves or flats depending. Bushings like Superpro, Whiteline and some of the newer offerings from Energy have features for controlled flex to avoid bind. Between these three they probably have an application for you.
Friday, January 15, 2016 1:21 PM
so when is this thing gonna hit the track?

also, why is it called Project "VA" WRX?
Friday, January 15, 2016 1:24 PM
if you go on SuperPro's website, they sell a ton of generic bushings that they list by measurements and not specific applications. so if you measure your part you may be able to find a bushing they already make with some "engineered flex" without having to cut it up yourself...
Tuesday, January 19, 2016 1:55 AM
@Mike Kojima
I have to disagree with the comment on page 4, picture 3. Although in most cases the shank is required to be longer to correct the roll centre, in this instance it is the housing that needs to be longer as the ball joint is mouted upside down to the more common way.
Tuesday, March 15, 2016 11:23 AM
Its been awhile since anyone has posted on this, and it is not totally related to this article, but what are your feelings about the brake torque vectoring that the VA WRX has?

I am not a big fan of brake torque vectoring for obvious reasons, but have you guys driven the VA hard for long enough periods of time to judge whether if it will negatively impact the braking system? And also if it can endure prolonged abuse?
Wednesday, May 03, 2017 5:10 PM
so I don't know if anyone will see this, but does this car have any cooling upgrades?
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