ST Suspensions Coilover Upgrade for WRX

Today our Subaru Impreza WRX gets a suspension upgrade with the ST Suspensions XTA coilover kit along with Whiteline Sway bars for improved handling and ride quality.

ST Suspensions is a division of KW Suspensions that features both KW damper technology and manufacturing for the best coilover kit to improve your handling and ride quality at an affordable price.  They provided their ST XTA Coilover kit – 18245802 compatible with 2002-2007 Subaru Impreza WRX with up to a 5-year warranty.

Whiteline provided their front and rear sway bar kit – BSK007M which includes a 24mm 2 point adjustable front sway bar and a 24mm 3 point adjustable rear sway bar.  This kit comes complete with high-quality sway bar end links and mounting accessories for maximum performance and easy installation.

You can see here the high quality hardware Whiteline provides with their swaybar kits for the GD WRX…along with a sneak peek at some of the other Whiteline goodies our GD project is going to be outfitted with.

Our Content Sales Manager, Ian Pak’s 2002 GD Subaru WRX has been suffering from a case of love, it’s been loved nearly to death! Over the years Ian has racked up over 208,000 enthusiastic miles and the car is badly in need of being gone through. We will be going through the car’s systems one by one upgrading them with some serious parts refurbishing the WRX into a solid track competent street car.  The first place we will be attacking is the suspension where we will be replacing the tired shocks with some quality coilovers from ST Suspensions and controlling body roll and dialing out understeer with some Whiteline anti-swaybars.

Many years ago while he was in school, Ian had done some suspension modifications replacing the stock shocks with some Tokico HD OEM replacement parts with Tein lowering springs. He had also installed a Progress 22mm rear sway bar.  The Progress bar is a good match for a stock front bar with mild or stock spring rates but we wanted to apply some of the lessons learned with our awesomely handling  STI Project GD to Ian’s car.

A long time ago this was a reasonable way to get more out of your suspension, nowadays there has been a lot of progress with how a suspension works. Compared to modern stuff, the progressive damping curve on the old Tokico’s is overly stiff and still does not offer the platform control of modern digressive dampers. Lowering springs tend to be too low and too soft, being a looks type of thing rather than a performance enhancement.  Many times, cars with lowering springs simply roll onto the bump stops in hard cornering which greatly reduces grip.  Usually, the front suspension bottoms first and the car will go into relentless grinding understeer.

Well, let’s get rid of this old, worn out 90’s technology and bring Ian’s car up to modern standards!

The front ST Suspensions coilover has a camber plate with a sealed corrosion resistant pillow bearing.

ST Suspensions XTA coilover’s damping is single adjustable.  The damping adjustment is in 18 steps.  The valving and internals use KW’s valve technology and is similar to a KW Variant II.  The front coilovers spring rate is 6.1 kg, this is considerably stiffer than the stock 2.9kg.  The lowering springs that were on the car were most likely only around 20% stiffer than stock so this is a huge step upward.  Modern damper valving makes the uses of stiffer springs without sacrificing the ride quality very much possible.

The body of the ST XTA Coilover is zinc electroplated steel with a yellow chromate coating for corrosion resistance

The plating of the shock body makes it highly corrosion resistant.  When combined with a stainless steel reinforced engineering plastic spring seat/adjusting collar you have a spring ride height adjuster that will not get stuck to the shock body with corrosion, even after a salty winter.

The rear spring rate is a progressive rate going from 3.9 to 4.1 Kg as the suspension compresses.  This is slightly stiffer than the factory spring rate of 2.9 Kg.

The rear coilover uses a progressive tapered spring and a special adaptor upper spring seat so the stock rear upper mount can be retained.

10 comments

    1. It looks like they discontinued the 27mm adjustable bars for this chassis which is a shame because they work pretty well on big tired and R compound cars. They currently offer 22mm and 24mm adjustable and non-adjustable varients.

      1. I did some checking and the 27mm bar is still offered for the STI. I can’t think why this would not fit on the base WRX. The part numbers are BSF36XXZ and BSR37XXZ.

  1. Super excited to see where this goes! I understand that ST suspension is designed and manufactured by KW, but was there any reason other than cost to go with this over KW? Also, I remember there being mentions of some power adders in the future. Are you guys cooking up something to deal with the not so torque friendly 5-speed or swapping out to the 6-speed?

    1. We decided to try the ST coilovers because we wanted to see how well they worked for a value-priced coilover set and we are pretty impressed. We are going to try to work with the 5 speed at first but are also mulling over the 6-speed swap at a later time.

  2. Any thoughts on upgrading to STi front control arms for improved castor? I’ve done this upgrade on my car (2005 saab 92x) when I refreshed the bushings and it made a great deal of difference. Went from 3.5 degrees of castor to 5.25.

    1. I believe the Spec C front lower control arms provide 5 degrees of caster, as well as JDM 2004-2006 or 2007 STi’s provide that same degree. I’m not sure how much caster increase the USDM STi’s would give me. Also, I believe SuperPro makes a control arm/Anti-lift kit combo that adds caster as well, but I’m not sure by how much.

  3. USDM 04/05 LCAs provide 5 degrees of castor (What I have on my car). Anything newer is 3.5. I don’t know much about the JDM arms.

    I’m not sure if the 06 WRX & STi LCAs are the same or just provide the same castor, but when the WRX switched over from steel to aluminum (in sedan form at least), that’s when the STi lost castor as well.

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