Project Subaru WRX STi Part 3: Streetable Track Worthy Suspension



Whiteline WRX/STi camber caster plate.
Whiteline’s camber/caster plate allows adjustment of both camber and caster, adding caster is critcal for the STi’s handling.

While we were in there we also installed a set of Whiteline caster camber plates in the front suspension. The caster camber plates allow adjustment in two axes so the camber and caster can be adjusted. The modified plate allows 1 degree more positive caster than any other plate on the market. The top strut shaft mount in the camber caster plate features a spherical bearing which eliminates the stock mounts sloppy rubber. Although this transmits a bit more noise, the lack of slop here helps keep the alignment true even though this is a highly loaded part when cornering. It also ensures that every bit of wheel up and down movement passes though the damper and is controlled.

With the caster camber plate in place we returned to West End Alignment and realigned the car to run 2.5 degrees negative camber and 6 degrees of positive caster, two more degrees of caster than we were able to get stock. This gave us a much improved on center steering feel and much sharper turn in. The cars once rubbery reflexes now felt sharp. If you remember in our first installment, rubbery, slow and unresponsive steering was the biggest dislike of this car in stock trim. With the additional negative camber and the lack of flex in the upper mount understeer was greatly reduced as well.

Our driving impression of the KW V3 coilovers was very favorable. In some ways the ride was much improved over the standard STi shocks and springs. Although the ride was firmer, the freeway chop and the seasick float of the stock suspension were reduced. The car had much improved steady state cornering and was much more neutral. The best thing we noted under track conditions was that the cars sudden transition to oversteer was further reduced with adjustment and the car became even more predictable with less of an on edge feeling even though the chassis was much more responsive to steering input. This is one of the best off the shelf coil over system for the STi on the market and perhaps the best riding system in every day street use that we have tried to date.

Whiteline XRD HD front swaybar for STi
The front XRD bar is a lot thicker than stock and straighter as well making it over 200% stiffer than stock.

To continue our upgrade path we next once again turned to the suspension.  We were planning to attend a NASA track day at Willow Springs and we wanted to have a more track ready suspension. In previous segments we had installed Whiteline’s basic handling package. Although we were pleased with the results we wanted to up the ante and take the car to the next level, the next level being near race car levels of grip and response.  We also wanted to take care of a few niggling faults that the car had in the suspension department as well.

Whiteline XRD STi rear swaybar
The Whiteline XRD rear swaybar compared to stock, note the adjustment holes.

The first step was to give the car some more roll stiffness.  Although the car had little body roll as is, we knew that we would get a lot more when we bolted on a set of soft R-Compound tires.  The tires additional stick loads the chassis harder.  To counter this we installed a set of Whiteline’s racing XRD bars.  The XRD bars are two way adjustable in the front and three way adjustable in the rear.  We believe that bar adjustability is important in a track car as it enables you to quickly adjust the car to changes from track to track or changing from high speed events such as track days to lower speed tighter work such as autocross.

Whiteline Heavy Duty rear swaybar mount kit for STi
Whiteline’s heavy duty swaybar mount kit prevents the rear swaybar from tearing out of the chassis


Whitelines bearing type end links
Whiteline’s bearing equipped end links directly couple the swaybars to the chassis, no lag or gush here!

The stout XRD bars are a whopping 27mm in diameter and over 160% stiffer than the handling packages 22mm bars.  They are also an amazing 280% stiffer than the stock 20mm bars.  We also installed Whitelines optional ball and socket solid bearing end links and heavy duty rear mount kit.  The bearings have length adjustment so they can be installed without preload which can affect handling balance from side to side.  Without the cushion of bushings they ensure that any body roll will be fully against the swaybars full torsional stiffness.  This greatly improves response.  To protect the bearings, Whiteline end links have a neat feature, dust boots. To prevent the stiff rear bar from tearing off the chassis, we also installed the optional heavy duty rear mount.  This is much stronger than the stock rear mount and should prevent the bar from damaging the rear suspension.  We set our bars at full soft in front and the middle of the three holes in the rear.

Whiteline sti rear sway bar in place
This shot shows the Whiteline XRD STi rear bar in place with the Heavy Duty rear mount.
Whiteline Sti rear sway bar in place
The front bar in place.


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