Project GD Subaru STI Part One- Rebuilding the Suspension

By Mike Kojima

The GD Subaru STI is an iconic tuner car.  The platform is highly developed and can easily generate supercar like performance for a really low price.  It is a well developed platform which has been raced in nearly every form from road racing to rally. A lot of development means that there are plenty of high quality parts available off the shelf for the car making it an exciting candidate for project car greatness.

Of course we have been wanting to do another GD project car since the white car from our early days of MotoIQ.  That car never got completed, it was in an accident and sat for a year while the owner decided what to do with it.  Finally he fixed it minimally and dumped it for cheap.

You can read about that car here

It was time for another car.  Our first car was an early 2004 STI.  This was the STI's first year and it had problems.  It had wimpy hubs with small bearings which quickly developed play causing brake piston knockback with an intermittent case of the brake pedal going to the floor.  The hubs had an odd 5x100 bolt pattern which limited wheel choices. It had a weak steering rack that developed play with soft, slipping mounts.  This made for an inconsistent steering wheel center and a mushy steering feel.  Finally the engine management had some quirks, it liked to detonate even at stock boost levels.

For that reason we selected a 2005 STI as the basis of our project.  Subaru had addressed most of the bugs in the first US market STI with stronger hubs and steering.  Now it was our turn to enhance the platform.  Our idea is to try and build the ultimate street going STI that is still practical for daily driving.  This means top notch handling and braking with out excessive harshness and poor short term wear.  No laggy or high strung engines with poor driveability and fuel economy would be acceptable either.

Still the car must be capable of going straight from the street to the track, be driven hard without going uncle and be driven home without having to mess with tire and brake pad changes.  To start our project we shopped for several months before finding our project car.  Unfortunately STI's are popular car to be modified and many examples are butchered with poor quality workmanship and parts.  Many more have been driven hard and put away wet by indifferent owners.

Our project car was a stock 2005 STI owned by a mature person who took meticulous care of it and kept excellent service records.  The car had changes of synthetic oil every 3000 miles for its nearly 50,000 miles of use and had never been driven in the rain!  The undercarriage and engine bay were like new. The paint and interior were mint.  STI's like this are very much sought after and go for a premium. We paid more than we wanted to but after looking at beat and butchered STI's for months, we just paid the 20k the owner insisted on and went on our way.

For our first installment of project STI we will set about building our suspension with some quality parts, fixing some of the STI's inherent weak points and taking care of 50,000 miles of wear and tear at the same time.  Our car had some very worn bushings in the suspension as the car made horrible banging and clunking noises when being driven over bumps and when starting, stopping and shifting so we decided to address these issues first with some quality parts from Whiteline. 

Whitelines bushings were developed for the extreme conditions of Australia's back roads and have some good engineering features like OEM quality steel retainer sleeves and engineered flex points to avoid binding when needed.  Whiteline bushings for this application come in three different hardness levels: Ride Comfort, Performance and Motorsports.  We opted for the hardest Motorsports grade as we felt that even hard urethane is more driver friendly than bearings.  We will report to you on our opinion of just how streetable the motorsports grade bushings are.

We wanted to switch out the old rubber bushings with some high quality parts produced by Whiteline.  Whiteline makes three grades of bushings for the STI, Soft but firmer than stock Ride Comfort, firmer Performance and hard Motorsports.  We opted for the hardest Motorsports bushings because they are still bushings after all, not something really hard like bearings!  The Whiteline bushings are really high quality.  Most of the bushings have an OEM quality steel shell to minimize the urethane thickness and to support the bushings like the OEM part.  This is unusual for an aftermarket urethane bushing.  The front lower control arm bushing is shown here.
Howard Watanabe of Technosquare presses out the old rubber bushing and presses in the Whiteline parts.  You should never burn out the old bushings like many people do with a forged aluminum arm like like the STI has.  Aluminum can lose its strength properties at the temperatures that burning out can reach and you don't want to weaken your suspension parts!
One of our tricks to reduce static friction with urethane bushings and to make them long term squeak resistant is to wrap the inner sleeve of the bushing with a layer of teflon tape.  The slippery teflon minimizes friction which improves ride comfort and mechanical grip.  It also prevents squeaking.  Whiteline bushings use a formulation of urethane that does not squeak as much as others but we still wanted to lower the friction.
 We apply the moly grease supplied with the bushings over the tape.
After greasing the inside of the bushing, we carefully push our taped and greased sleeve into the bushing. This ensures a smooth ride and squeak free use even with the hard Motorsports bushing.



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Wednesday, July 04, 2012 11:26 PM
The best mod I ever experienced on an STi was a Q-Rack (http://www.q-rack.com/). I loved it.

It would be interesting to see a different tuning solution than Cobb for this project. We know it works well, but other people may not know about all the great open source tools and options for Subaru.

Curious to see what bushing you thought was the hardest to replace? Having access to a lift and a press seems to make them all a piece of cake. I have had to take parts off and bring them to a shop to get pressed, if the crazy Home Depot bushing removal contraption I end up making does not work.

Lastly, it would be interesting to see some other high quality brands (besides Whiteline and KW)on this project and be able to compare and contrast to other and past cars. Such as Ohlins, Beatrush, Cusco or maybe even Subaru community grown companies like RaceComp Engineering or Turn In Concepts.

Whatever direction you go, I can't wait to see more of this one.
Mike Kojima
Mike Kojimalink
Thursday, July 05, 2012 1:08 AM
The Q-rack sounds like a good idea! I will be contacting them as one of the reasons why I like the Evo over the STI so much is it's really quick steering.

The diff carrier bushings were the biggest pita's on the car. Getting rid of them got rid of the horrible banging around we were having back there so it was worth every penny. The funny thing is the hard motorsports bushings did not change NVH one bit over the softer bushings.

Our priority is to work with quality companies that want to work with us. We are having a hard time finding other mid price suspension companies to work with because they are not many of them around and ones we find only have limited applications or they are not in financial shape to work with this us.

In my opinion the crappy coilover companies have pushed many of the better companies either out of business or upmarket. The crappy coilover companies have more money to market and sponsor drivers and are free with product for the magazines. Unfortunately the stuff we have gotten to test doesn't work so we chose not to write about it.

The bottom of the market is flooded with really crappy coilovers and we won't go there. We have had bad experiences when we tried and wasted our time with a few.

We are trying but its hard to find other suspension companies that offer as good performance as KW for a decent price point. Being a suspension engineer, I am always amazed at how well KW's work for both the street and the track. It's so good its hard to find stuff that works in the same range for the price. KW has such a large range of applications, it seems like they have something for every car we do something with.

Our "love" for KW is genuine, they make good stuff and if you would not be pleased with it, believe me, we would not be writing about it. I think our staff has the credentials to give a good opinion about this stuff.

There are high end companies that make very good stuff but they are often not willing to work with us as their volumes are low and they are semi custom parts. We hope to get Ohlins and JRZ on some of our projects soon.

If anyone knows of a good suspension company that wants to work with us, send them our way! We are desperately trying to find other good companies to work with.
Dan DeRosia
Dan DeRosialink
Thursday, July 05, 2012 3:35 AM
Turn In Concepts developed a coilover with AST (who bought Moton) so there's decent odds there... they also took the unusual step of documenting the development, including publishing dyno plots as they went. Worth taking a look at IMHO. RaceComp Engineering has a coilover that's done by KW to their specs, so might also be worth taking a look as you can be pretty assured the build quality's going to be there. Feal (Odi Bakchis) has a coilover now; Taiwanese but supposedly with higher quality internals specced; they seem to me to be the least expensive Subaru coilover I'd be willing to take a chance on. He also does revalves of the STI strut inserts and has always been really responsive to questions; for that matter, all three that I mentioned have been pretty open with the Subie community.

Anyway, just mentioning a few potentials other than KW you may or may not have run across. Not that there's anything wrong with KW, but more because it would be interesting to some of us to see if there *is* other stuff that stacks up.

Speaking as someone daily driving a bugeye, I look forwards to seeing where this project goes.
Dan DeRosia
Dan DeRosialink
Thursday, July 05, 2012 5:44 AM
Speaking of KW, and poking at the writeup of the previous try where the KWs are dissected a bit, why coil springs on the blowoff valving? Is there some provision for adjusting the preload on the springs to change where the knee comes in? Coming from having spent a bit of time trying to fit either Penske or Bilstein based monotube valving into struts, all this twin tube stuff looks weird to me. ;)
Thursday, July 05, 2012 6:35 AM
I know they dont get a ton of credit in the industry but I've had TEIN Flex coilovers for 5 years and 100,000 miles on my IS300. I'm sure some of their other lines beyond the Flex would be more oriented with your STi Project goals. I also know they do (or did?) stateside repair, refreshing, and custom rebuilding.

In my time with these coilovers I've been very happy. They ride well, perform well, havent blown out (knock on wood) and have gone through snowy/salty Minnesota winters. There is little to no corrosion and I honestly feel I've gotten my moneys worth and then some. Just thought I would throw it out there as an option if you guys havent really considered thme.
Julian ITR
Julian ITRlink
Thursday, July 05, 2012 7:28 AM
This article made me curious about the next installment of The Ultimate Guide to Suspension & Handling, I would like to learn a lot more about anti features, like when you want them and how much, and what the drawbacks are (also regarding drivetrain layout).
Mike Kojima
Mike Kojimalink
Thursday, July 05, 2012 8:58 AM
We have asked Tein if they want to be involved with what we do numerous times as we feel that they are one of the only quality coilover manufactures but they tell us they are not budgeted to do so. Typically Japanese companies get very conservative when times are tough. We really want Tein to come on board. Cusco too.

I am friends with Odi and have been taking to him about doing some stuff for us for while. We have some really terrible coilovers lying around and we were trying to get some time and a car to have to work them over for us to evaluate.

The blow off coil spring preload on the compression side is adjustable on twin tube KW's. I am not a shock engineer but I assume a coil spring is used because adjusting the preload is more linear than cranking on a washer stack. KW has some new technology were overall metered fluid volume is changed via orface size which is coming soon and we will be evaluating that.

For this car we are getting a really trick but affordable coilovers from KW. They are not your typical clubsports but something all new at a good pricepoint for the performance they offer. Stay tuned, we will have the first set in North America.

We will look to other companies to try and get the best stuff we can.
Boro Drift
Boro Driftlink
Thursday, July 05, 2012 9:51 AM
Mike, what are your thoughts on Fortune Auto's coilovers?
Mike Kojima
Mike Kojimalink
Thursday, July 05, 2012 11:16 AM
I just checked out their website and it looks promising. I sent them an email and I hope they get back to me. It looks like a potentially exciting combination of decent quality Taiwanese parts and good calibration and service.
Dan DeRosia
Dan DeRosialink
Thursday, July 05, 2012 11:38 AM
That's another one I'm kind of hopeful about... reviews from forumites seem favorable, but then again what do they, on average anyway, know?
Thursday, July 05, 2012 12:19 PM
Ohlins are a slightly higher price point than KWs, but for sure good quality. Well, IMO.
Mike Kojima
Mike Kojimalink
Thursday, July 05, 2012 1:15 PM
They are single adjustable.
Thursday, July 05, 2012 4:08 PM
Yes, the Ohlins Road and Track series are only single adjustable and come in at the same price point as KW Clubsports which are double adjustable. But not everyone needs double adjustable; so depending on the skill and knowledge of the end user, the Ohlins and KWs are direct competitors.
Mike Kojima
Mike Kojimalink
Thursday, July 05, 2012 4:10 PM
Double adjustablity of damping is highly useful.

Thursday, July 05, 2012 9:02 PM
Mike, I agree with you on the coilovers. I had custom valved Clubsports on my GR STi (RaceComp Engineering Tarmac 2) and loved every moment of them. If I were to ever buy coilovers for a daily driven Subaru again, KW would be at the top of my list. Probably the only thing on the list.

I thought because you have so much experience with them, it would be interesting to hear a knowledgeable comparison between their products and another quality company like Ohlins and such. I think as a community, we already know that any KW you throw on a Subaru is going to be really good. However I understand the constraints you work under.

I think you will love the Q-Rack. I had a 12.5:1 and it was so enjoyable. It was on a daily driver in Los Angeles and I never thought the ratio was overly quick.

Thanks for the commentary on the bushings :)

On a related note, I would love to see what a well prepared 2.5 Subaru can do with the newer Tomei Arms M8265. I feel Tomei is overlooked by the Subaru community, at least in the USA. Their turbo kits and header build quality look really nice and thought out, engineered even. People see the knock-offs and not think it's worth buying the Tomei because they are "expensive".
Mike Kojima
Mike Kojimalink
Thursday, July 05, 2012 10:52 PM
One thing that I find about the higher end "Euro" shocks, be they KW, Ohlins or Moton (the ones I have direct experience with) is they all have a similar feel.

They have very little of that vague float feel which I think is valve response time and very good low speed control. So these shocks all have that firm but not harsh feeling. These shock all have adjusters where you can really feel even one click of adjustment.

Japanese dampers, and old school good stuff don't capture that feeling and they tend to be floaty and harsh at the same time. I think this is due to slower responding valves and a lack of low and mid speed damping. Most Japanese tracks and roads are so smooth that perhaps they never had a need to super well developed dampers.

Cheapo coilovers are just horrible some of them feel like there is no oil in the case and the knobs don't do much if anything.
Friday, July 06, 2012 7:26 PM
I know you guys didn't change anything visible from the outside but what gives with having absolutely no shot of the car itself?

Also, very very excited. The 2005 STI is about the greatest looking one they made and having fixed all of the issues in the "beta" version in 2004 it is one of the few I would consider buying.
Mike Kojima
Mike Kojimalink
Friday, July 06, 2012 11:05 PM
When we wrote the story the car was taken apart. If you want to see what it looks like, find a picture of a stock 2005 STI and there you have it!

What sucks about 2005's is that everyone wants one so they are hard to find. They are plenty of 2004's on sale.
Dan DeRosia
Dan DeRosialink
Tuesday, July 17, 2012 12:10 PM
Wow, I'm a moron; rereading this and I realized I somehow missed your response to stuff I asked.

I should have figured you'd know Odi, but you never know... be looking forwards to seeing what you have in store there. The coil spring blowoff I'm tempted to run some numbers on from the drawings to get a feel for what it's doing. Not necessary in the real world, but I got really interested in stuff like that after starting down the road of DIY struts (problem of roadracing a car with no good strut options) so forgive me if I wander off into weird technical tangents. ;) The orifice size metering sounds interesting; sorta like the old Penske 8100 canister adjusters in concept, but hopefully they work better... hell, I can't imagine KW would bother without being aware of the strengths and weaknesses of what came before.

A new offering from KW sounds pretty damn exciting, especially since I find myself seriously considering them. The big issue locally is rough roads and salt in the winter, and having something that doesn't rot off the car, and is valved by people who know how this stuff should work. Looking forwards to more!
Mike Kojima
Mike Kojimalink
Tuesday, July 17, 2012 12:31 PM
It sort of looks like Moton/JRZ/AST style metering but I only got a brief look at it. I am flying to KW Germany in a few days to get briefed on the new stuff.
Dan DeRosia
Dan DeRosialink
Tuesday, July 17, 2012 12:55 PM
Well, conceptually, there's only a few ways to do these things. Of course, in the process of looking this stuff up (wasn't sure of the number) I found out that Penske actually advertises that they'll sell people roadrace style struts now (as opposed to the drag ones) so yay, way to invalidate the need for some of what I was trying to do... now to just sell a couple kidneys.
Mike Kojima
Mike Kojimalink
Tuesday, July 17, 2012 1:36 PM
I tried getting some stuff from Penske a few years ago and their tech support guy was very rude and condescending to me. I got so angry I asked the guy if they even cared about my business and the guy told me that they are busy with Indy, F1 and WRC so they could care less about my business.

So perhaps this was just one a-hole working for a great company but they will never have my business or endorsement due to their horrible treatment of me. I was asking professional level, non-stupid questions and was very polite until he made me mad so I dunno.
Dan DeRosia
Dan DeRosialink
Tuesday, July 17, 2012 2:57 PM
Ouch. Never had a bad experience, but then I never tried to get ahold of their tech support for anything; the whole project got to where I was pricing out what it would take to get seamless tube in the right size before I had more important things to get working come up.
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