Subdriven | The Subaru Enthuisast Website

For most people, going to the racetrack usually brings to mind images of open wheel racers, stock car bodies, tube-framed race cars, and pretty much anything that has very little resemblance to the cars the most people drive on the street. While this may be the popular image of racing, there are many enthusiasts that drive relatively stock or modified vehicles in various avenues ranging from high performance track days to local autocross and rallycross events.

In recent years, there has been a boon of people buying sporty cars and getting more and more involved in motorsports. Partnerships between companies such as the SCCA and Subaru, where free SCCA memberships are offered when someone purchases a WRX, have done a great deal to enhance the experience. As such, the WRX has quickly become adopted by many as a favorite combination for daily driving and weekend racer.

While the WRX has a competent suspension, most weekend racers find it too compromising and lacking the traits necessary to be competitive on the racetrack. Such issues can be addressed in many different ways. Solutions may range from simple quick-fix attempts ranging from changing sway bars and struts or adjusting alignment specs to try to become competitive. Others may want the ultimate possible performance and go for an all-out, no-compromise coilover system.

Given the many options, choosing a suspension can be a difficult task, especially since there are very few compromises available for those seeking top performance and the ability to keep the car as a comfortable daily-driver. While having the fastest or best handling car at the track is great, having to pilot a car that feels like its always driving on a washboard isn’t always the most desirable situation.

Enter Praxis Advanced Suspension. Praxis, a division of Bridgestone, have taken it upon themselves the task of engineering a do-it-all suspension. At their state of the art facility, they have utilized their experience with air suspensions and combined elements to create a suspension that goes from the “Street to Track With A Button”.

An obvious question is how can going to an air-based suspension actually help? Most people (myself included), when they hear the term air suspension, think of big rigs or perhaps, one of those SUVs that has a similar system in order to help when towing or carrying a heavy load. So how does this work in a performance application?

The design of the Praxis system is quite intriguing. The suspension makes use of air springs combined with inverted and adjustable monotube struts. That means this system isn’t your typical air-based system that uses air in conjunction with a separate standard spring system. Combined with a unique piston design, the Praxis air spring will increase the progressive rate as suspension height drops.

Even better for the track day warriors, the suspension is designed to automatically handle corner-weighting. Of course, adjusting the height of the vehicle will change alignment, but Praxis provides specifications for a custom alignment that considers the changes the suspension experiences when adjusting height. The suspension does add weight - about 25-30 pounds - but the weight has been strategically distributed to optimize placement of the various components, such as the air compressor, dryer, and reservoir.

Praxis suspension consists of:
- Adjustable, inverted-monotube struts (4)
- 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)
- Cock control module
- Brackets for air reservoir, compressor, ECU, valve block, and height sensors
- Air plumbing
- Installation hardware
- Detailed instructions

Suspension modes:
The Touring mode provides ride height, characteristics, and handling traits that are comparable to those provided by the vehicle's original suspension. This mode provides the most comfortable ride qualities for weekday commuting, weekend touring and long vacation trips. It also preserves the vehicle's original ground clearance to enhance its mobility when driven through deep snow or on secondary roads.

The Sport mode reduces vehicle ride height by 25-mm as compared to the Touring mode and increases spring and shock damping rates to reduce body motions and sharpen steering response. This mode provides a more aggressive appearance along with sportier ride characteristics and more responsive handling traits than the vehicle's original suspension for fun, enthusiastic driving on twisting roads.

The Track mode reduces vehicle ride height by an additional 25-mm, virtually doubles the original spring rate, and specifies the firmest shock damping rates to maximize stability and handling response. This ultimate performance mode provides the most aggressive appearance along with performance for autocross and track driving situations. The no-nonsense Track mode is not recommended for street driving or, for that matter, the faint of heart.

How does it perform?
The slogan “Street to track with a button” is a little bit deceiving. To adjust modes, one really should do more than just click the button, as that merely changes the spring rate. Damping should be simultaneously adjusted or you’re likely to be displeased with the resulting handling characteristics should you choose not to do so. Fortunately, this step can be easily done without any tools. Adjusting the shock damping requires you to basically get down on the ground, reach for the bottom of the strut, and adjust a certain number of clicks. Once done, and after adjusting spring rate from the inside, you’re ready to roll. The process is actually easy enough, although the truly lazy among us (myself included) would love everything to happen at the click of a button. But as that would likely add even more to the already hefty price tag, it seems rather reasonable for Praxis to present the system this way. Keeping a towel, newspaper, cardboard, or tarp nearby can come in real handy unless you don’t mind getting your back dirty.

The suspension, even in Touring mode, has a distinctly different feel compared to the stock WRX suspension. While remaining comfortable and soft, the Praxis suspension provides a noticeable improvement in turn-in with a mixture of a firmer reaction and what seems to be a loose area where the car feels floaty during slight transitions. However, in Touring mode, the car definitely feels more confidence inspiring while maintaining the daily driving characteristics desired by most.

Jumping to Sport mode drops you down a little bit and provides a noticeable change in driving characteristics via a little bit firmer ride along with quicker steering response.

The real gem is Track mode. Track mode drops you a full 50-mm lower than stock, and the suspension gets noticeably stiffer, although not truly bone-jarringly stiff. The car begins to feel just the way you want it to; providing great responsiveness while remaining completely composed under aggressive driving with minimal body roll. Changing to the Track mode seems to qualm some of the quirks of the standard suspension and yields a much more neutral-feeling WRX.

What’s it worth?
A major criterion in deciding the value of a suspension system is not merely how much it costs, but whether or not the system delivers in the end. No doubt the Praxis system does not come cheap. At the time this article was written, this suspension costs $3450 from the Tire Rack. Thankfully, Praxis designed this system to be easily installed by a DIY mechanical person, so those that are inclined don’t need to spend another several hundred dollars on installation. Buying a suspension that costs this much is not an easy matter, but for the versatility and levels of performance offered combined with the ability to drive every day in comfort, a very tempting offer is made. While many people may be hesitant to spend more than $1500 on even the very best coilovers, even those who do will lose the adjustability that makes the Praxis suspension system so great.

We welcome any comments from actual Praxis suspension owners who use this versatile solution in the real world.