In six short weeks, Richard Stanboli and the Team Cycle World Attack Performance crew have built two Kawasaki ZX-10R AMA Pro American SuperBikes and four ZX-6R Daytona SportBikes. During that same time span, riders Eric Bostrom and JD Beach have tested variations of those machines at Daytona International Speedway, Las Vegas Motor Speedway, Buttonwillow Raceway and Chuckwalla Valley Raceway, all in preparation for the opening round the 2011 AMA Pro Road Racing season at Daytona International Speedway, March 10-12.
The Chuckwalla test was held under clear, blue skies one week after the team returned from Buttonwillow. Neither Bostrom nor Beach had ever ridden the 16-turn, Ed Bargy-designed, 2.68-mile circuit, which has become a popular testing spot for AMA Pro teams. In preparation, Stanboli had modified the 10R’s stock rear suspension link, dramatically altering its leverage ratio to move dynamic balance toward the front of the motorcycle.
Stanboli had also finished an American SuperBike-spec engine, which, on the night before the test, produced 201 rear-wheel horsepower on Attack’s dyno—a 12-hp leap from the LeoVince exhaust/MoTeC ECU-equipped-but-otherwise-unmodified powerplant that Bostrom rode in January at Daytona. In addition, the latest bike has a new wiring harness custom-built by Dan Schwartz of the Attack Tuning Center.
The modified link was a huge change. Bostrom returned to the pits after just one lap and said, “It’s really stiff, like a strut.” Öhlins Road Race Manager Mike Fitzgerald—who had been living in Southern California and working out of the Attack Performance shop for so many weeks that I wondered if he’d considered buying a home here—steadily moved through a staggering number of damping, spring and ride-height combinations in hopes of finding the desired front-to-rear balance.
As part of the process, Fitzgerald had brought along two bathroom scales, onto which mechanics Jim Matter and Todd Fenton rolled the 10R. With Bostrom seated on the bike, helmeted head tucked behind the tiny windscreen, the scales read 275 pounds front, 274 rear. Minus the rider, the numbers were 206 front, 180 rear. “Ideally, you’re looking for 55-60 percent of the weight up front,” said Fitzgerald.
On-track, progress came in waves. From my notes: “EBoz is complaining of ‘big, rolling movements from the front end. Drivability is out the window. When I get on the throttle, the fork extends and starts running off the track.’” Later: “Biggest improvement all day. Bike is starting to hold its attitude.”
Stanboli wanted to lengthen wheelbase, but the rear axle was already shoved as far back in the stock swingarm as it would safely go; the ZX-10R swingarm is 20mm shorter—580mm vs. 600—than that of the Suzuki GSX-R1000 that we raced at four AMA rounds last season. Kawasaki’s factory World Superbike racers run longer-than-stock custom swingarms; AMA rules require stock arms, with no modifications to the pivot.
More changes, more comments: “The bike is so close to being stellar,” said Bostrom. “But I can’t carry corner speed. I can’t keep the nose down and drive through the center of the corner. The good thing is, if we can get around this track, we can get around any track.”
Bostrom was impressed with the new Brembo T-Drive front brake rotors, whose stainless steel swept area floats on eight T-shaped pins rather than conventional cylindrical buttons. “Biggest performance gain I’ve felt in brakes in a long time,” he said. “The old rotors had a little wobble; these are dead-straight—amazing.”
While Bostrom was sorting out the 10R, Beach was cutting laps on a ZX-6R that was stock-engined but fitted, like the SuperBike, with Öhlins TTX25 gas-charged cartridges and a fully adjustable TTX36 shock. Initially, Beach was having a tough time getting his bearings. “The track is so flat,” he said, “I can’t find any markers.”
Once the 19-year-old was up to speed, chatter stopped his progress. After switching from a medium- to a hard-compound front Dunlop, he chopped a full second off his previous-best lap time, at which point the chatter returned. “This track induces chatter on a 600,” said Fitzgerald. “You’re leaned over for a long time, carrying a lot of speed.”
After lunch on the second day of the two-day test, Bostrom finally threw a leg over the Daytona SportBike-spec machine that he will race in the Daytona 200. He spent the rest of the afternoon swapping back-and-forth between the two bikes—not easy.
At times, progress with the 10R seemed to stall. “Man, if I didn’t know better,” Bostrom told Stanboli and Fitzgerald, “I’d think that was the same fork setting we ran yesterday. The fork is always trying to extend—pow! pow! Bostrom’s lap times on the 10R nevertheless continued to fall, eventually dipping into the mid-1:48s—nowhere near the 1:43.9 track record set a week earlier by Rockstar Makita Suzuki’s Tommy Hayden.
“This is the challenge of being a one-rider team,” said Bostrom. “You just run out of time. It’s really easy to make the bike fun to ride, but you give up all of the performance. If you try to make the bike ‘edgy,’ it just gets angry.”
“You knew this was going to be a challenge when you signed up for it,” replied Stanboli. “I knew it, too. But we’re going to get it.”
With the sun setting and track temperature dropping, Bostrom rolled into the pits for the final time and cut the engine. He turned to Stanboli. “It’s the best bike yet. I felt like I could slide the bike, get out of shape and recover. Daytona doesn’t have any bumps. If we can just hold the back of the bike up on the banking…”
As Bostrom walked away, Stanboli looked down at the bike, his focus strong. “I think we have a direction now,” he said.
We’ll soon see.