Project VA WRX: Finishing the Suspension With Superpro

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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