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| Whiteline’s roll center correction kit also corrects bumpsteer. |
To round out our EVO’s suspension, we also installed Whiteline’s roll center correction kit. One of the reasons why we love Whiteline is that they are one of the only companies to address suspension geometry issues. In short when you lower a McPherson strut suspension car, the center of gravity gets lower which helps reduce weight transfer to the outside wheels, a good thing. When the suspension is lowered, the CG height above ground goes down but the roll center also gets lower dis-proportionally, dropping more than the CG. The roll center is a virtual point in space that the car rolls about and it is determined by geometrically projecting the relationship of the suspensions pivot points. The distance between the center of gravity and the roll center increases giving centrifugal force a bigger lever arm to roll the car over under cornering force.
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| The Whiteline roll center correction kit uses a balljoint with a longer shank that drops the outer control arm pivot point to raise the roll center on a lowered car to a close to stock location. |
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| The Whiteline tie rod ends lower the steering pivots to correct bumpsteer in the steering geometry. |
The other issue is if the car is lowered to the point where the lower control arms are pointing upward from the inner pivot (which they nearly always are in a lowered car) the suspension will lose negative camber under roll and the tires will lose traction. Thus a lowered car will roll more and have less front grip unless really stiff spring rates are used which reduces ride comfort and can increase tire shock which also reduces grip.
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| Howard used a hydraulic press to remove the stock ball joint from the control arm and press in the Whiteline part. The press was also used to press out the stock front inner control arm bushings. |
The Whiteline kit uses a special ball joint with a longer shank to drop the outer pivot point of the lower control arm. This raises the roll center to a close to stock location and improves the camber curve when the car is lowered. Relocating this pivot point increases bump steer, not good, so Whiteline provides tie rod ends with longer shanks that correct this issue! Now you can have proper suspension geometry with a lowered car, a Whiteline exclusive!
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| These urethane bushings replaced the stock rubber parts. The Whiteline bushing has good attention to detail, serrated ends on the inner sleeve to help lock it in place and grease retention grooves to reduce squeaking. |
Finally we installed some of Whitelines hard polyurethane bushings in the front position of the lower control arm. The stock bushings are run in the rear. This gives the suspension toe out under load which reduces understeer.
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| Our teflon tape trick works for bushings as well! |
With our new suspension the EVO handles and even rides better. It can be adjusted from street soft to track stiff in minutes and the understeer can be dialed out when on the track. Our EVO X is now crying out for stickier rubber which we will address soon now that our suspension can be adjusted to take advantage of it.
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| Our front suspension is ready to rock! |
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| Our locked and loaded rear suspension. |
Stay tuned, we have much more in store for our EVO X in installments to come!
Sources
Global Performance Parts (US distributor for Whiteline)
