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That is pretty neat, but one question I have is how well does this system control things like toe, camber, etc? It is my belief that when you lower a car there is more to change than the dampening characteristics.

With camber and toe affected you are actually decreasing the amount of tire tread on the ground.
 

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2nd try: CPU/Chip mods for the STi

This is way cool. :D

I think I found my only suspension mod. Todd, they probably came across that issue and found a solution for it. I don't think they would've introduced this other wise. Bigger question is how much?
 

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Discussion Starter #5
91TB78 said:
That is pretty neat, but one question I have is how well does this system control things like toe, camber, etc? It is my belief that when you lower a car there is more to change than the dampening characteristics.

With camber and toe affected you are actually decreasing the amount of tire tread on the ground.
I could be wrong, but you don't change toe by lowering a car, do you? That would mean that as the suspension is compressing during normal driving, the toe is changing.

Camber will just be a by-product of the lowering. There's nothing you can do about that in a fully adjustable system like this. With a static system such as coilover or shortened spring kit, you'd just adjust the camber with the stock adjustment. I've never heard of an auto adjustable camber kit.

I wouldn't worry about the camber though. If you are truly using the kit for the intended use, that would be awesome. For street/highway, you would have most of the camber out, but then when you want all the camber (autox, road course), it would be there.
 

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True..I don't know why I mentioned toe in the first place..just being spacy. Yeah, I guess it might not be too bad, but I think it would depend on the range of drop..if it is much more than say 1.5"-2"s its going to change camber quite a bit.

Of course with a nice Tein kit, or whatever, you would lower ride height and then with the camber plates adjust accordingly..so I dunno.
 

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Discussion Starter #7
True. You would be able to dial in the camber you'd like, but it would be relative to each setting.

I run about 1 degree negative camber on the rear and I can only get 7/8th in the front on my Celica, and I haven't seen any wear problems. My buddy who is even more serious in autox than I am runs 2 degrees on the street. Of course the handling is amazing, but the wear isn't so hot and braking/acceleration is hurt a little, but not too much.
 

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BOV/Wastegate Info

CloNeGTS said:
I could be wrong, but you don't change toe by lowering a car, do you? That would mean that as the suspension is compressing during normal driving, the toe is changing.
hmm. i was under the impression that toe and camber would change. it seems like "bump steer" (where the car steers itself due to suspension movement) might suggest that toe would change. (???)

http://www.racerpartswholesale.com/longtech3.htm
 

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CloNeGTS said:
If you are truly using the kit for the intended use, that would be awesome. For street/highway, you would have most of the camber out, but then when you want all the camber (autox, road course), it would be there.
i *wonder* if maybe the same thing can be said about toe. when it's lowered, you get more toe-in, which is what you'd want. these interactions of ride height and camber and toe would be *very* specific to the geometry of the suspension, so it's hard to generalize what car x would do. dunno.
 

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CloNeGTS said:
Has anyone seen this thing yet? Before you assume what I did, airbag setup.....read this website.
didn't the old subaru xt6 have *something* like this? friends of mine had one. they said it was outrageously expensive to replace a corner. apparently many owners converted over to coilover suspensions when their went bad.
 

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Discussion Starter #11
4MLA1FN said:
CloNeGTS said:
I could be wrong, but you don't change toe by lowering a car, do you? That would mean that as the suspension is compressing during normal driving, the toe is changing.
hmm. i was under the impression that toe and camber would change. it seems like "bump steer" (where the car steers itself due to suspension movement) might suggest that toe would change. (???)

http://www.racerpartswholesale.com/longtech3.htm
Bumpsteer doesn't have to do with suspension travel itself. Bump steer relates to steering linkage and the fact that if poorly designed, compressing the suspension actually changes the geometry of the linkage. This would have absolutely nothing to do with the rear of a car either.

Bump steer is something that was common on older, low performance cars. There is no way a car such as the STi could have bumpsteer in the design. Such a defect would be noticed by anyone testing the car and would be an embarrassment to a vehicle such as the STi.
 

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Discussion Starter #12
4MLA1FN said:
CloNeGTS said:
If you are truly using the kit for the intended use, that would be awesome. For street/highway, you would have most of the camber out, but then when you want all the camber (autox, road course), it would be there.
i *wonder* if maybe the same thing can be said about toe. when it's lowered, you get more toe-in, which is what you'd want. these interactions of ride height and camber and toe would be *very* specific to the geometry of the suspension, so it's hard to generalize what car x would do. dunno.
A properly designed suspension shouldn't change toe as the suspension is compressed. This would make a car very unstable if it was the case. The suspension travel of any corner should act so that the wheel doesn't not change in how parallel it is with the long axis of the car. Go jump on the corner of your car. Does the tire "spin" on the ground? It shouldn't.
 

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Digging up an old post...I was re-reading my Nov '02 issue of Import Racer that features a black WRX modded in Irvine, CA with help from SPI Motorsports and Greddy...and it had an adjustable Tein suspension: Ten Type Flex coil-overs with Tein Electronic Dampening Force Controller (EFDC) so that you can adjust it on the fly from the driver's seat. Reminded me of this Praxis System but this one has 16 settings as opposed to 3 (not like you'd be able to use all 16 but it's nice to know you have that flexibility).

Question is, how good are Teins? Seems like they're a pretty good system and since this Praxis System (new and under development??) isn't even available yet, I was considering this for my WRX, and also wondering if they're a significant improvement over the stock STi's
 

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Discussion Starter #15
You're adjusting a few more things with the Praxis that the Teins cannot. The Teins would allow you to change comp/rebound on the go, but not ride height. That's the cool thing about the Praxis....it's both of those.

Teins are amazing units...but they are pretty complex to setup right. Even with all the adjustments, it would take a decent amount of testing to get your settings right. I don't think they'd necessarily be better than the STi suspension, but it would allow you to make the car *dampen* the car exactly as your driving style would allow.

Keep in mind...a setup like Teins would be a stiff system and I don't think it would have the amazing forgiveness the STi system seems to have in the rough stuff. But setup up properly....it would be mean.
 

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Re: Now here's a gauge pack

I emailed Praxis a couple months ago and just got an email today on the update...MSRP $3695, available August 1, 2003. Here's the email:

Hello again,

It has been quite a while since the last Praxis product update. Over the
past two months, our team has been extremely busy finalizing the engineering and production details of the Subaru WRX system. We have also been preparing for a media event and product introduction at Willow Springs Raceway. This event will introduce the editors of many popular enthusiast publications to the Praxis system and will allow them to experience the product on both public highways and the race-track environment. Expect to see independent reviews published in two to three months.

Our web site (www.praxissystems.com <http://www.praxissystems.com>) will be updated shortly to reflect the technical specifications of the final product. Until that occurs, I have included a FAQ list to address common questions.

Q: What does the Praxis system do?
A: Praxis allows the driver to select the height, spring-rate and damping
for whatever driving adventure lies ahead. There are no coil-springs to
change and no spanners to carry, because the spring-rate and ride-height is controlled by air. It's as easy as touching a button and turning a knob.
Select one of three programmed ride-heights and spring-rate levels with a
simple push of a cockpit mounted button. Then adjust damping by turning the adjuster conveniently located on each strut-unit. Touring mode, Sport mode or Track mode ... you control the level of performance.

Touring mode: Touring mode provides ride and handling comparable to the factory delivered vehicle. Original ride-height, spring-rate and damping produce a balance that is perfect for daily commutes or highway touring.

Sport mode text: Sport mode dramatically steps up handling responsiveness. Ride-height is lowered one inch. Spring-rate and damping are increased to reduce body motion and sharpen steering response. The vehicle is now ready for your favorite canyon road or an enthusiastic jaunt to work.

Track mode: The ultimate performance setting, Track mode lowers the vehicle two inches, doubles spring-rate, and provides the firmest damping of all. A no-nonsense, no-compromise setup for the most aggressive autocross and track driving situations. This setting is not recommended for street driving or for the faint of heart.

Q: What is included in the Praxis system?
A: The Praxis system includes all components necessary to convert your
vehicle. The system has been designed to be application specific in order
to ensure proper fitment and avoid performance and installation issues often encountered with "generic" aftermarket products. Praxis products are properly packaged to avoid damage during shipping and include a
comprehensive set of instructions to ease installation. A comprehensive
list of system components is provided below:
· Externally adjustable, inverted-monotube struts (4)- co-developed and
manufactured by H&R
· Multi-Rate air springs (4)
· Air compressor
· Air dryer
· Trunk mounted, auxiliary air reservoir
· Valve block
· ECU
· Multi-axis accelerometer
· Height sensors (4)
· Wiring harness (pre-assembled with fuses and relays)
· Cockpit control module
· Brackets for air reservoir, compressor, ECU, valve block, and height
sensors
· Air plumbing
· Installation hardware
· Detailed instructions

Q: How does the Praxis system differ from other aftermarket suspensions for the Subaru WRX?
A: The aftermarket offers many opportunities for the performance enthusiast. There are many existing coil-over products that enhance the track performance of the Subaru WRX. Unfortunately, a properly tuned motorsports suspension is a poor choice for a road-going vehicle. Day-to-day usability demands a suspension that can absorb road inputs encountered on typical public highways (pot-holes, cracks, speed-bumps, etc.) and it is in these everyday situations where the existing aftermarket products suffer. Praxis has created a new product category, the advanced suspension, which allows the user to enjoy a compliant suspension in everyday use AND a properly tuned motorsports suspension when the situation demands.

Q: Does raising and lowering the vehicle affect wheel alignment?
A: It is well known that toe and camber change as ride height is altered.
Our alignment specification (different than the factory specification) will
allow daily use of touring and sport modes without affecting tire wear.
When the car enters the track mode, the camber becomes more aggressive (negative) ... this is good for lap times and will not produce undesirable wear considering the race-circuit environment. Randomly choosing an aggressive camber angle without regard for toe setting or other suspension characteristics usually results in rapid and irregular tire wear. Bridgestone technology has enabled us to use state-of-the-art methods of predicting tire wear to optimize the alignment setting to balance both handling and tread life. You will not have to realign the car when you change ride heights. You will need a one-time alignment when the system is installed.

Q: Why does the Praxis system include an accelerometer?
A: Since the Praxis system was designed specifically with the performance
enthusiast in mind, it was necessary to produce a product that performed
flawlessly on a racing circuit. The accelerometer serves this function by
providing the ECU with information about how hard the vehicle is being
driven. In turn, the ECU can make informed decisions about when to add or remove air from an individual spring. The presence of the accelerometer avoids allows the ECU to intelligently decide whether a suspension motion is originating from forces that demand air movement (i.e. adding cargo or changing operating modes) or from forces that do not warrant movement (i.e. high-g cornering or skid-pad testing).

Q: How can the Praxis system automatically corner-weight the vehicle?
A: Because the Praxis ECU and valve-block can control airflow to, from, and between the air-springs mounted at individual wheel-positions, we have been able to develop a control sequence that automatically re-distributes air between springs during a height-change. This re-distribution results in balanced diagonal weights, and a car that handles symmetrically in right and left turns.

Q: How much does the system weigh?
A: The system adds approximately 30 pounds to the weight of the vehicle.
The increased weight comes mostly from the air-supply system (compressor, air tank, valve-block assembly) and is equally distributed between the front and rear of the vehicle.

Q: How long will it take to install the system?
A: Installation of the Praxis system is somewhat more complex than the
typical strut installation because of the air-line plumbing and electrical
wiring that must be routed through the interior of the vehicle. We have
simplified the installation by providing fully assembled strut units that
can simply be bolted in place and a wiring harness that is fully
pre-assembled. All brackets are application specific, so no fitting,
adjusting, drilling, welding or soldering is necessary. Fully detailed
instructions will guide a moderately accomplished amateur through the
installation process in eight to ten hours. No special tools are required,
but the vehicle will require a suspension alignment after the installation
is complete. The Praxis warranty will be valid whether the system is
user-installed or professionally installed.

Q: What is the Praxis warranty?
A: We will warrant the air-strut units (springs, struts, mounts) for
2-years. All remaining components are warranted for one year. Best of all, we will warranty the system for sanctioned, amateur motorsports applications (autocross, Solo-I, Solo-II, rallycross, lapping days, drivers schools, drag-racing) ... this is an industry first.

Q: How much does the Praxis system cost?
A: The Praxis system for the Subaru WRX has an MSRP* of $3,695. *MSRP = Manufacturer's Suggested Retail Price

Q: When can I purchase the Praxis system?
A: The WRX application will be available for public purchase Aug 1, 2003.

Q: Where can I purchase the Praxis system?
A: The Praxis system will be available for retail purchase at The Tire Rack
(www.tirerack.com <http://www.tirerack.com>, 1-888-541-1777)

Q: What applications will the system fit?
A: We are introducing the product on the WRX platform. This application
will fit model year 2002+ Subaru Impreza 2.5RS, WRX, WRX-STi sedans and wagons. We will add applications as our engineering resources allow. In the near term we will focus on Sport-Compact and Sport-Sedan platforms that have high aftermarket interest. It is our intent to add two additional applications in early 2004.

Thank-you for your continued interest,

William S. Niaura
PRAXIS Advanced Suspensions
Manager - Marketing & Technology Coordination
1200 Firestone Parkway
Akron, OH 44317
 

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UPDATE: I just checked the website last night and it stated that tirerack.com will be selling this system for about $3500 starting Aug 4th!

For the STi setup, the touring setup will actually RAISE the ride height...would make it a more comfortable daily driver :)
 
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