The Motorbike Archives

Theories about the ideal stadiumcross bike design abound in the pits. Each has its champion of reason, for each team has struggled to find the right combination of factors required to overcome the apparently contradictory requirements of stadium racing; each is confident that the answer has been found. Some bikes work reasonably well and many show a hint of success, but by seasons' end most riders are on board a trusty outdoor bike and the engineers have scurried back to the drawing boards.

The problems of stadiumcross bike design lie in four major areas. First of all, building the bikes themselves is both a philosopher's dream and a diplomat's nightmare, for each individual part must function in a spirit of compromise due to the peculiar nature of stadium tracks. Secondly, the motorcycle's mechanic must be able to maintain whatever trickery the unfamiliar stadiumcross machine might incorporate while still being able to properly attend to his rider's outdoor bike. Third, the riders need bikes that they can adjust to quickly and easily, for the stadiumcross format doesn't allow hours of practice and familiarization. And finally, even the largest factories do not have enough money to develop a motorcycle design exclusively for stadiumcross.

To really understand the stadiumcross bike, you must first understand the tracks themselves. Nowhere in the motocross world are motorcycles as brutalized as on a stadium track apparently designed solely to catapult bikes as high into the air as possible. The impact registered by the suspension after falling straight down from 10 feet in the air is tremendous. Dave Osterman, who wrenches Mike Bell's Yamaha, notes, "The spring rate is critical, and indoors Mike needs a much stiffer suspension."

Apparently, then, the first parameter of stadiumcross bike design would be long-travel suspension with stiff spring and damping rates capable of handling the vicious drop-offs and monstrous whoops. But then you must provide for hairpin corners that require nimble handling. The ideal stadium bike must be capable of changing lines in the tight turns in order to pass under crowded racing conditions. And this requirement suggests a bike with a low center of gravity that can be flicked from side to side. It also points toward a bike with shorter suspension travel to minimize front-end dive in the corners to keep steering precise.

Suzuki built a few short-travel supercross specials late in 1978 for just these reasons, but by late in 1979 they had been abandoned. Explains team manager Mark Blackwell, "Early in the year we ran those bikes and did pretty well. We were able to turn faster lap times. But then the riders would get too tired." Apparently, a shorter-travel bike has its advantages, but few riders can withstand the pounding they must endure as a consequence. A few riders like Kawasaki's Jeff Ward still prefer a shorter-travel bike for stadium races, however. Comments Mark Johnson, Ward's mechanic, "We lower the Uni-Trak as far as possible and turn the axle cam (Kawasaki's unusual rear axle mount) so the bike sits lower."

With shorter travel requiring many sacrifices in performance, some riders have attempted to make their bikes turn easily while maintaining full suspension travel. Suzuki's Mark Barnett raises the fork tubes in the triple clamps for a steeper steering-head angle. Tuner Doug Grant says, "The Suzukis need to have the rake pulled in on these tracks with such tight turns, and it also makes the wheelbase a little shorter, which helps in the tight sections."

So far, the whoops and hairpins can be handled with a combination of strong legs, strong-suspension and quicker steering, but what of the high-speed straights filled with ruts and invisible bumps, waiting to provoke tank-slappers that spit riders on their heads? Too-quick steering geometry makes the front wheel sensitive to deflection, after all. When the engineers don't have the answer to this problem, it's up to the riders to keep the bike pointed straight. And basically, it gets down to what Tony Di-Stefano says: "You gotta keep the gas on and hang off the back of the bike and keep the front end light."

Once the suspension has been dialed in and the handling sorted out, the engine is next. Matching gearing and powerband is critical, yet stadiumcross tracks have conflicting priorities. The engine must twist out lots of horsepower at high revs for the all-important start, while providing enough low-end and mid-range punch to keep from being outgunned in the tight infield corners. Every rider seeks a different combination.►

◄Kawasaki rider Warren Reid asserts, "The start is the most important part of stadium racing and I really want good power." Maico star Danny Chandler does it differently, as mechanic Bill Deprado explains, "We've gone to a different barrel-and-pipe combination. What we want is lots of midrange." Jeff Clark, Scott Gillman's tuner, says, "We've been looking for good low-end punch for coming out of the tight turns and then we play with the gearing until it's just right."

The task of turning the total package into a bike greater than the sum of its parts falls to the mechanics. Their job is already arduous, for from the time they receive factory prototypes early in the year until the time they discard the trashed remains at the end of the season, they twist wrenches constantly. Consider that they must provide a bike that is both competitive and reliable, yet at the same time they must test new developments from the factory engineers. And once you understand that some riders like Jeff Ward might require three different bikes every year—one for 125 Nationals, another for Stadiumcross and another for the Trans-USA, each of different displacement—you begin to realize how difficult it is to sort out the peculiar problems of a stadium bike.

Now that you're thoroughly confused about the stadiumcross bike formula, there's one more variable to throw into the equation: The riders themselves must adjust their riding styles to fit stadium circumstances. From the outdoor tracks that they practice and ride on five times a week they go to a track that is much shorter, tighter, packed with more traffic and filled with more dangerous obstacles—not to mention the tension-filled atmosphere of the stadiumcross. Sliding a rider onto a bike that is both radical and unfamiliar can compound the problems of bike design. Chris Hines, who attends Suzuki rider Brian Myerscough's bike, reports, "We don't really do too much to the bikes anymore, while other wrenches make the bikes more radical. I think it's more important to make it easy to ride." Adds Myerscough, "I think it's better to have a bike that I'm used to and have confidence in."

The real bottom line of stadiumcross bike design just may be money. The builders must decide if they can afford to devote their R&D sections to months of testing and thousands of dollars of fabrication to build a bike that will never be sold to the public. The logistics of shuffling a team of race bikes around the country are already complicated. The Yamaha team has nine riders this year. In addition to their regular mounts, the Yamaha riders get a special bike for Supercross plus a back-up. Getting all these bikes in the right place at the right time with the necessary spare parts while allowing enough time for testing provides an open invitation for a dance with Murphy's Law.

As it turns out, though, the factories are devoting more energy to stadium bikes as the series expands. And indeed as long as the seats are jammed and the pot at the end of the race overflows with gold, the manufacturers, tuners and riders will continue to struggle with the stadium bike, and the starting line will be filled with the latest in stadiumcross trickery.■