Playing with cars is a one-way street. The machines start out stock but are soon modified to go faster. Then they're modified again to go faster yet, and the process repeats until someone runs out of money, time, or desire. It's a fundamental fact of automotives.
Nowhere is this truer than with race cars. Drivers and cars start out simply-innocently, even. Left unchecked, they end up as sweating adrenal glands, gushing flames from the Bonfire of the Bank Accounts. The challenge for those stewarding the racing is to maintain the flames of passion without incinerating the host. For NASA, the National Auto Sport Association, the strategy is to offer a trilevel playing field to V-8 road-racing enthusiasts, especially Mustang owners. The three steps are Camaro-Mustang Challenge (CMC), American Iron (AI), and American Iron Extreme (AIX).
Step one, the Camaro-Mustang Challenge, we've chronicled before, but to recap, it allows basic chassis modifi-cations such as wheels, tires, springs, bushings, brake pads, and so on, and nearly nothing to the engine other than open exhaust. Thus, CMC Mustangs run totally stock engines, right down to the original, heavily crimped factory headers. With 240 hp or so at the flywheel, CMC cars are still plenty entertaining to drive, and the concept has proven popular on the West Coast for several years.
Inevitably, however, the CMC troops were ready for more power and handling. Enter American Iron, which, as NASA's step two, almost immediately became its most popular V-8 class. The idea was to give CMC racers a class to move up to, but it has also become a strong draw for those looking to move straight into wheel-to-wheel road racing from the street or open tracking. Cleverly thought-out rules make this an easy jump for many enthusiasts.
Conceptually, the American Iron rules start with CMC basics but allow engine modifications, along with more generous chassis improvements. Critical cost-containment provisions are provided, including a stock bodywork stipulation, a 9.5-lb/hp rule, and a spec tire coupled with a maximum 17x9.5-inch wheel. Together with liberal rules on many other aspects of the chassis and engines, these restrictions go far in capping costs, while not crimping the car builder's creativity. They also make American Iron extremely friendly to the aftermarket, as competitors are free to choose from a huge number of parts or systems, rather than being forced to run specific part numbers mandated by the sanctioning body.
Consider the wheel, spec tire, and associated fender-clearancing rule, for example. Fenders must remain stock-no adding or cutting material for flaring, and no tubbing-but they can be rolled or otherwise clearanced. Furthermore, NASA picked the Toyo RA-1 as the spec tire. Practically speaking, that means a 275/40-17 tire is the workable limit.
A relatively durable unit that lasts three race weekends, the RA-1 obviously saves costs by suppressing the need to buy stickier, but shorter-lived, tires every weekend. But by limiting wheel diameter, along with tire width via the fender limitation, these rules also allow NASA to legalize any brake that fits inside the wheel. With a 17-inch maximum, that means the popular and relatively affordable Motorsport 2300-K kit, or the equivalent 13-inch designs from Baer Braking Systems, Brembo, or the like, is where everyone ends up. Thus, by simply stating the wheel and spec-tire dimensions, the tires, wheels, and brakes are taken care of while leaving the owner plenty of room in which to experiment. This is a big help considering most people moving into American Iron already have some modifications done to their cars, and they don't want to obsolete their existing aftermarket parts.