Project EVO VIII part 4, Getting More Trackside Grip, Killing Some Slip


Whiteline EVO rear bump steer kit
Whiteline’s rear suspension bumpsteer eliminator kit relocated the position of the toe arms inner pivot by using the offset steel sleeves in the thinnwalled urethane bushings.
Whiteline EVO Steering precision kit
Whiteline’s EVO steering precision kit (part number KCA390) eliminates the soft rubber bushings that the steering rack sits in and slightly raises the rack to reduce bumpsteer.
Whiteline EVO roll center correction kit
Whiteline’s EVO roll center relocation kit (part number KCA395) consists of ball joints and tie rod ends with extended shanks.

Bump Steer Reduction, Roll Center Relocation and Steering Precision Kits
Although the EVO has a well-designed suspension, when the car is lowered, some of the geometry in the rear gets slightly out of kilter.  This has to do with the location of the toe links in the back. The toe links swing through a different arc than the rest of the suspension causing the rear wheels of the car to steer themselves as the suspension strokes.  This phenomenon is called bump steer.  Bump steer can make the car feel twitchy in the back at the limit and under trailing throttle.

Whiteline EVO bumpsteer reduction kit
The bumpsteer kit installed in the toe arm.  You can see how rotating the eccentric moves the pivot location.
Whiteline Roll Center Correction kit
As installed you can see how this simple part really changes where the pick up point mounts.  It makes a big difference in stability.

To reduce the rear bumpsteer we installed Whitelines bump steer correction kit.  Whiteline is an Australian company that has an impressive array of suspension components for many Japanese cars including most Hondas, Toyotas, the WRX, Nissan S13/314 and Sentra SE-R’s.  Whiteline also has many geometry correcting kits for cars that need it, an unusual detail for a suspension component manufacturer.

Whiteline’s bumpsteer elimination kit for the EVO relocates the position of the inner pivot of the tie rod upward. The kit consists of a urethane bushing with an internal eccentric. This puts it at a more favorable angle so it does not allow the toe to change much as the suspension strokes.  This simple and inexpensive part makes Project Evo much more predictable, especially in bumpy turns.

We used Whiteline’s steering precision kit to mount our EVOs steering rack.  The kit replaces the rubber bushings holding the steering rack with hard Urethane and moves the rack up slightly to reduce bump steer.  The kit is designed to impart a more solid steering feel and improve the secure feeling of the steering when traversing bumpy surfaces.

Whiteline Roll center relocation ball joint vs stock
You can see how much taller the Whiteline roll center ball joint is when compared to the stock part

Whiteline’s roll center adjustment kit was also installed in the front suspension.  This unique and innovative product is a boon to making your EVO handle well.  We are used to having to hand fabricate this sort of part on our racecars but Whiteline has simplified it to make it a bolt on product for the EVO.   The roll center adjustment kit uses a ball joint with a longer shank.  This effectively moves the lower control arm outer pivot downward and raises the roll center.  In a lowered car, the roll center drops and the roll couple which is the lever arm for centrifugal force to roll the car over when cornering gets longer.  Thus a lowered car sometimes exhibits more body roll than a car at stock ride height all other things being equal. The Whiteline kit is designed to move the roll center to close to the stock location on a lowered car.  This reduces body roll and makes the car more responsive to steering input.


Whiteline evo roll center relocation tie rod vs stock
You can also see how much longer the shank is on the Whitleine ball joint compared to stock


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