Rumors of the telescopic fork's death have been circulating since the late 1970s. Still, the venerable tele lives on. Refined, tweaked and optimized, today's beefy, inverted, nitride-plated cartridge units would nonetheless be instantly recognizable to any Norton mechanic circa 1938.
Where just about every other part of the modern motorcycle has evolved, far from its roots, somehow here in 2007 we've still got the fork. Miraculously, it's still found on the front end of every championship-winning Grand Prix racer. How can this be? Mainly because it works. And with the application of immense design and materials technology, it works really well.
But suspension designer James Parker believes we can do better. He's doing all he can to hasten the "end times" of the fork. And his latest prototype, the GSX-RADD P3, is ready to accelerate the process.
Parker puts it this way: "About 70 years of refinement has kept an outdated design alive. It'd be like the car guys hanging onto the live axle they've had since the covered-wagon days. If you applied the latest technology and materials-carbon fiber, titanium and computer modeling-you'd probably end up with a really good live axle." But that wouldn't make it any less of a relic. That's because the double-wishbone and multi-link alternatives are so much better.
The fork has had a hell of a run, and as motorcyclists we've all either learned its quirks or fallen off a lot. By virtue of our learned programming, a fork is a large component of what makes a motorcycle feel like a motorcycle to us. But Parker believes we're satisfied with it only because we know nothing of life beyond the fork. Fighter pilots in 1943 no doubt thought their P-51 Mustangs were the bomb. But they hadn't flown an F-86 Sabre in '51. Or an SR-71 Blackbird in '66. In a few short years, the game can change completely. And when it comes to front suspension, the game is long overdue for change.
From an engineering standpoint, the fork frankly sucks. Since it's so tall, loads at the front tire contact patch are greatly magnified by the time they reach the steering head. That means the fork and frame must be fat and heavy to resist the forces. And much of that structural weight is far from the machine's center of gravity, further slowing the bike's steering response. And since the entire fork assembly turns with the front wheel, it adds considerable mass to direction changes. Stiction-the binding of the inner and outer fork tubes due to bending loads-makes the suspension less compliant. And the fork also adds to front-end dive under braking, since the wheel travels rearward as the suspension compresses. The more braking Gs you pull, the harder it wants to squat. We could go on, but your eyes would glaze over.
Parker has been working out the solutions to these problems since Ronald Reagan was still slapping Nancy on the ass. In broad strokes, Parker's four unique front-suspension prototypes, a Yamaha production bike and a heap of patents spanning 25 years share some key features. First, the front wheel is carried on an automotive-style upright. The upright provides a mounting point for the front brake caliper(s) and pivots on a pair of suspension arms-one high and one low. The position of the suspension arms has evolved over time to meet the demands of MotoGP-caliber lean angles, conventional steering lock for low-speed maneuvering and room for big, dual-disc brakes. The lower arm in Parker's designs has migrated from about axle height to a position just above the brake discs. All versions of his RADD front suspension have a single-sided lower arm that allows the wheel to be removed without disturbing the brakes or suspension, as on an automobile.