RACING FORWARD, CAREFULLY; the Nextel Cup Car of the Future takes form.(Competitions.)

Byline: BILL McGUIRE

Gary Nelson wants you to think evolution, not revolution. As NASCAR's managing director of research and development, he leads the effort to create the Nextel Cup "car of the future,'' a five-year project begun in 2002 and scheduled to be track-tested sometime next year. While the name suggests something, well, futuristic, the car of tomorrow in "stock car'' racing looks an awful lot like the car of today, especially at first glance.

That is by design, according to Nelson. If it ain't broke, don't fix it, and as far as NASCAR is concerned most of the car ain't broke. "In many ways we have learned that what we have works just fine,'' says Nelson. "This isn't change just for change's sake.''

So Nelson's working prototype, constructed at NASCAR's Research and Development Center in Concord, North Carolina, looks much like today's package. A steel ladder frame welded up from rectangular tubing supports an elaborate space frame/roll cage running the length of the car. While the hardware is custom fabricated, the front suspension and steering geometry can be traced to the 1964-72 Chevelle, while in the rear a venerable nine-inch Ford live axle is suspended by coil springs and located by trailing arms lifted from a 1960s Chevy pickup. There is a cast-iron pushrod V8, naturally, though its final specs are yet to be determined. "We're not ready to make a definitive statement about that yet. It's too soon,'' says Nelson. It is all familiar: NASCAR's car of the future is based on the heirloom chassis, which is itself based on several decades of evolution that just sort of happened, one lesson at a time.

So what will be new? Probably the most visible change is in the roll cage and greenhouse structure, which is both taller and wider (mostly wider) than in the present car. There are three benefits: First, the prouder roofline increases aerodynamic drag to slow speeds somewhat. NASCAR likes the aerodynamic qualities of its Craftsman Truck Series vehicles on the big speedways-lower speeds, less tendency toward "aero push''-and would like to emulate them in the next generation of Nextel Cup cars. Next, the wider, taller cage affords greater impact protection to the driver, who will also be seated further inboard for even more safety. Finally, the taller roof allows the size of the driver's window to be increased, for quicker escape in the event of an accident. The tiny window openings and tight roll cage dimensions in today's slick, downsized body styles make it difficult for normal-size drivers to ...