Riding on Air
Today you want to take your BMW 3-Series for a 400-mile drive to a vacation home by a mountain lake, but next weekend you'd like to drive that same BMW in a local Sports Car Club of America autocross competition. Does that present a problem? It does if you'd like to make that long drive to the mountain lake in comfort or if you want to win the autocross, because with a standard suspension, if you want to do one, you simply can't do the other.
Until now, that is. The Praxis line of adjustable, performance, air-suspension systems allows the driver to control performance -- on the road or at the track -- without the need for tools or time in the shop. And while you might not be interested in competing in any auto-related events in the next few weeks, the technology also presages a future in which suspensions can be adjusted -- or even adjust themselves -- depending upon driving conditions. For example, think of a sport utility vehicle that is tuned for great on-pavement ride and handling, but also has a suspension that adjusts to give it more suspension travel and softer springing when it is moving slow in off-road mode. The technology is nearly in place to make that a reality.
How does Praxis work? It employs multi-rate air-spring technology, coupled with the Intelliride control-system and externally-adjustable monotube dampers supplied by H&R Springs to allow the driver to rapidly select the ride-height, spring-rate and damping. A simple touch of a cockpit mounted control button and a simple damper adjustment at each corner places the vehicle into one of three fully-tuned operating modes.
Currently there are Praxis systems for the Subaru WRX, Ford Mustang and BMW 3-Series. Each delivers the drivers a choice of suspension tuning. For example, the BMW system for the 3-Series features three modes -- Touring, Sport and Track. Touring mode provides ride and handling comparable to a base BMW 3-Series vehicle. The original ride-height, spring-rate and damping produce a balance that is perfect for daily commutes or highway touring.
Sport mode dramatically steps up handling responsiveness, allowing the vehicle to perform much like the highly developed M-3 model. Ride-height is lowered, while spring-rate and damping are increased to significantly reduce body motion and sharpen steering response. Sport mode allows the enthusiast to tackle a favorite twisty road while enjoying the pleasures of a tuned, responsive chassis.
Track mode, the ultimate performance setting, is appropriate for a variety of amateur track events. In this setting, the vehicle is dramatically lowered, while spring-rate and damping are increased to track appropriate levels. Track setting is not recommended for extended street driving.
The Praxis system for Mustang is also tri-modal, but in addition to the Touring and Track modes, a Drag mode optimizes drag strip performance by adjusting spring-rates and ride-heights "on-the-fly" to optimize launch traction and high-speed aerodynamics.
"Our systems expand the operating range of the BMW and Mustang, while avoiding the compromises associated with typical aftermarket suspension upgrades. The adjustability of the Praxis system allows the amateur motor sports enthusiast to have one vehicle that is an equally competent daily driver and track vehicle," said John Vincent, managing director, Praxis Advanced Suspensions. "The Praxis development process harnesses the engineering talents of the global Bridgestone organization to deliver a fully tuned and optimized suspension system that has been designed and tested to OEM standards. For example, the performance of the Praxis fitment for the BMW 3-Series will be validated through testing at the challenging N