Whiteline's steering precision kit reduces bushing flex and bumpsteer by relocating the st
For the rear suspension we used Works rear pillow ball mounts. The Works mounts do away with the factory stock squishy rubber mounts, replacing the rubber with a spherical bearing held in an anodized billet aluminum housing that bolts to the body. The bearing allows the suspension to articulate smoothly while assuring that every bit of movement is controlled by the damper. Low speed control takes place at under 2 inches per second velocity and the stock rubber mounts can stretch and allow up to 1 inch of vertical shock shaft movement. With superior dampers that work well at these low velocities, it's easy to understand why solid high-quality mounts are important.
Whiteline's roll center kit helps raise the roll center on lowered cars, reduce bumpsteer
Of course we cannot overlook the springs. After consulting with Robi on spring rates we chose 2.2-inch Eibach ERS racing springs. Eibach ERS springs are available in a tremendous array of lengths and weights, which makes a suspension tuners life much easier. We settled on 7-inch long 550 in/lb front and a 650 in/lb rear springs with a 200 in/lb tender spring. These spring rates are nearly three times stiffer than stock but are still considered on the soft side for track use. The tender springs are bottomed out with the cars weight on them but they come into play by helping keep the car's inside wheels on the ground in real hard cornering. This helps forward traction on the exit of turns. Although a stiffer spring rate is often used on the track, a chassis without a cage cannot easily make use of rates much higher than this. If the springs are too stiff then the cageless chassis flexes and becomes a giant undampened spring, which can contribute to tire shock. Robi's philosophy is to use soft compliant springs to allow the suspension to work and to limit roll by using stiff anti-sway bars and by raising the front suspensions roll center.
You can see how much taller the Whiteline roll center ball joint is compared to the stock
When it came to anti-sway bars we naturally used Robispec adjustable units. The Robispec bars are 25mm up from the stock 24mm for the front bar with two adjustment holes and 26mm up from the stock 22mm for the rear bar with four adjustment positions. The front bar can be up to 80 percent stiffer than stock, depending on which hole it's adjusted to, and the rear bar up to 140 percent stiffer, depending on which hole is used. The Robispec bars come with urethane mounting bushings and the rear bars come with a heavy-duty chassis bracket that better withstands the stress of the thicker bar. The bars also have adjustable end links featuring spherical bearings rather than the stock plastic ball and socket joints. It is important to get rid of bar preload after corner weighting.
When setting up a car at the track, unless you have a big pit crew, performing a spring change to change the balance of the car in the time allotted between run groups is nearly impossible. However, it's pretty easy to adjust the sway bars to change the cars balance. Setting the car up stiffer in the rear and softer in the front increases oversteer or decreases understeer. Stiffening the front bar and softening the rear decreases oversteer or increases understeer.
Look at how much longer the shank is on the Whitleine ball joint compared to stock.
Robi made sure we addressed other details necessary in building the ultimate EVO suspension. We replaced the front lower control arm bushings with harder Energy Suspension polyurethane bushings. The rear lower control arm bushing is a high-quality rubber mounted spherical bearing and following Robi's advice we left it stock, however Energy does make a hard urethane replacement for this part with a special tapered center bore to allow it to articulate.
We used Whiteline's steering precision kit to mount our EVO's steering rack. The kit replaces the rubber bushings holding the steering rack with hard urethane and moves the rack up slightly to reduce bumpsteer. The kit is designed to impart a more solid steering feel and improve the secure feeling of the steering when transversing bumpy surfaces.