GSX-RADD: Hub-Center Steering
Sandia Motorsports Park is a scrappy little motorcycle track on the outskirts of Albuquerque. It wasn’t the snakes that worried me; for a place surrounded by miles of empty desert, there was not much runoff.
"How does it feel?" James Parker asked after I’d had a couple of sessions to acclimatize to the layout and begun to get up to speed.
"Light," I said. "It is light," he replied. "It’s 22 pounds lighter than the stock bike." "No, that’s not what I meant," I explained. "It doesn’t feel light for a 1000; it feels like a 250."
Parker has been on a mission to replace the telescopic front fork since he fell in love with motorcycles as an Industrial Design student at Stanford in the 1960s. He club-raced in the ’70s.
"Back then," Parker says, "forks were terrible." But, as primitive as those damping-rod forks were, they were better than the only real alternative-the hub-center steered suspension on the Elf Honda Grand Prix bikes, as designed by André de Cortanze. Those motorcycles had poor ground clearance on one side and, like almost all systems with a steering arm, they were prone to bump-steer.
Parker devised a collapsible steering shaft that ran down the steering axis. "I quit racing," he told me, "when I filed that first patent. The legal costs were about the same amount as a season on the track, and I couldn’t afford both." His first test mule was powered by a Honda 600cc single.
Parker took it to the Honda’s American headquarters in 1984. The company had just signed a young rider and it sent the kid-his name was Wayne Rainey-to Willow Springs to test the bike. Rainey was impressed, but Honda told Parker it preferred to keep working with de Cortanze.
A Yamaha FZ750 motor powered Parker’s next prototype. That bike-dubbed the MC2-appeared at the 1987 Milan Motorcycle Exhibition, and in magazines all over the world. Yamaha was deluged with inquiries.
At the same time, product planners in Yamaha’s European headquarters were pushing the company to develop a flagship sport tourer. The brief for the GTS1000 included ABS, electronic fuel injection, and Parker’s RADD suspension. It should have been his big break, and he cannot conceal his bitterness over 20 years later.
"I’d go to Japan for meetings," he told me, "and they’d wheel a prototype into a boardroom. The guys I spoke to never had dirt under their fingernails." He warned them that changes made to the steering geometry would hamper the bike’s handling.
When the GTS was finally launched, it was an expensive barge; the ABS and EFI didn’t work any better than the suspension. Only a few thousand were sold. The motorcycle industry’s conclusion was that alternatives to the front fork did not sell.
Parker retreated to Santa Fe, N.M., where he still lives in the same modest 1920s-era bungalow. There are two motorcycles in the living room; there is no evidence that anything has ever been cooked in the kitchen. There are books everywhere-history, pulp fiction, art and design, conspiracy theory. He passed his time designing motorcycles for a variety of resurrections-Indian, Vincent, and Indian again.
"I wasn’t pushing it, looking to file more patents, it just all came together," Parker told me. "In 2006, I realized that there were some aspects of the fork, mainly the geometry, that were good. And I realized that I could make a suspension that would feel like a fork, but offer the advantages of a hub-center steered suspension, too."
Parker literally went back to the drawing board, and found two other outsiders to help him. Juan Romero works at Sandia National Laboratories.
He scanned Parker’s hand-drawn designs, converted them to CAD files, and sent them to his club-racing buddy Jonathan Butterman, a machinist for the high-tech and defense industry.
Check out the underside of that lower suspension arm. That is 40 hours of CAD programming and CNC machine time by Romero and Butterman. In mass production it would be a die-cast part-stronger and even lighter.
Manufactured that way, a RADD suspension would cost a little more than a typical fork, but nowhere near as much as, say, an Öhlins race fork. Parker bent and welded the front subframe, made of steel tubing, in his driveway. Between the three of them, there is not a single engineering diploma.
This time, Parker was determined to test his theory on something other than a bloated sport-tourer. For use as a test mule, Suzuki gave him a GSX-R1000 K7 they had kicking around. To build the prototype, he borrowed against his house. That is the bike I crossed a thousand miles of desert to ride.
About half of Sandia’s turns are taken in first; there are only a couple of places where you can get over 100 miles an hour, and then only for a few seconds. The surface is riven by deep seams, bumps, and choppy asphalt. There are a couple of near-jumps where the course enters and leaves a stock-car oval. While I would not want to race there, it is a good place to test a road bike’s handling.
I alternated between Parker’s GSX-RADD and a stock version of the bike. Both motorcycles have the same wheelbase, rake and trail, exactly the same ergonomics and controls, the same brakes and motor, and the same rear swingarm. In order to show off the inherent stability of the prototype, neither was fitted with a steering damper. The differences between the bikes showed up immediately.
The first turn is a 180-degree banked right, part of the oval track. Thanks to its dramatically reduced steered mass, the prototype takes less steering effort and seems more responsive to body input. The racing line takes you across two deep pavement seams that upset both bikes; the prototype settles much more quickly.
Next up is an increasing-radius right that leads up to a very tight hairpin left. Although the RADD bike dove less under braking than its forked sibling, it was easier to adapt to than, say, a BMW Duolever setup. It was exceptionally good when trail-braking.
The local club-racing #1 plate holder tested the prototype and reported that, even though it was equipped with Dunlop Qualifier road tires, he could brake later on it than he could on his slick-shod race bike.
Parker has gone to a lot of trouble to make his suspension feel like a fork. Nonetheless, the experience is totally different. On cold tires, the gnarly surface of that hairpin is intimidating. It was here that I noticed the prototype’s most striking trait-I could feel the texture of the asphalt.
It was confidence inspiring, but I was always aware that I was riding a self-funded one-off prototype. Had I crashed and destroyed Parker’s suspension, it would make spending the next couple of nights on his couch pretty awkward. So, I came away impressed, but also relieved to return the prototype in the same condition it was in when I took it out.
Side-by-side, the most visible difference between the two bikes, besides Parker’s radical-looking front end, is the side-mounted radiators on the prototype. They create room in front of the motor for the upper suspension arm.
"Radical." Parker hates that word."RADD stands for Rationally Advanced Design Development," he told me. "Everyone thinks it’s Radical, but it’s Rational." His design may be rational, but he has pursued it, to say the least, single-mindedly.
There was a snowdrift of unopened mail on the dining room table when I visited. Walking to breakfast on the Santa Fe town square, I almost had to jog to keep up-maybe that’s because he is used to hiking in the nearby mountains twice a week, or because he is running out of time. Parker is in his 60s, so he cannot wait much longer for the motorcycle industry to give his hub-center steering system a second chance.
Here is the rub-although motorcycles are about 100 times riskier than cars per mile traveled, the motorcycle industry, particularly in Japan, is very risk-averse. Senior managers do not dare challenge orthodox wisdom. They will test Parker’s GSX-RADD only when they believe ignoring it is the riskier path. If they think one of their rivals might be getting a two-year head start on the next big handling breakthrough, Parker’s phone will start ringing again.
In the interim, Parker would love to find a Moto2 team willing to take a chance on it. That spec-motor formula, which replaces the 250cc class in support of MotoGP this year, would be the perfect place to demonstrate superior handling.
James Parker is ready to lead us out of the forking wilderness. Having ridden his bike, I am a disciple. Considering how good the GSX-RADD is at this early stage in its development cycle, every major sport bike manufacturer should evaluate it. The line forms on the right.