Öhlins has attached suspension technician Matt Hickson to Team Cycle WorldAttack Performance Yoshimura Suzuki. Hickson started his career with the Swedish suspension manufacturer packing boxes and sweeping floors in the warehouse of its North Carolina U.S. headquarters. After hours, he began to ask questions about dampers. In time, working under the guidance of veteran Mike Fitzgerald, among others, he learned new skills and was given fresh responsibilities. He’s now a regular at AMA nationals.
Hickson has responded well to this new challenge. The pressure associated with this type of work is high, yet he works quickly and capably without hesitation. At Mazda Raceway Laguna Seca, second stop in our planned four-round schedule, Hickson was beginning to get a grip on rider Eric Bostrom’s on-track needs.
“Eric doesn’t like the bike to move back and forth a lot,” he said. “Mid-Ohio has a lot more ‘jerks’ in the turns from hard braking and getting back on the throttle. Here, the track is smoother with nice sweeping corners. We’re trying to make the bike feel more supple and smooth versus being so ‘bound up.’”
Öhlins has supplied our team with its latest NIX fork cartridge kits ($1320 per fork). These utilize the stock fork sliders and stanchions, as mandated by current AMA Pro American SuperBike rules. We were also issued a pair of fully adjustable TTX36 shocks ($1403 each; CW Evaluation, April, 2009), one for each of our two GSX-R1000s.
Ohlins’ Matt Hickson prepares to make a spring change on the Team Cycle World Attack Performance Yoshimura Suzuki AMA Pro American SuperBike. With the NIX cartridge kits, rebound damping is controlled exclusively by the right fork leg. Compression is on the left.
“NIX is pretty simple—one side compression, one side rebound,” explained Hickson. “It’s a lot easier to work on than the previous 25mm kit; each leg had a compression and a rebound stack. NIX has fewer functioning parts and is easier to service. Performance is still there; adjustability is still there. With the other system, once the bushings and sliders wore, bits and pieces could clog the smaller 2.5mm holes. With these kits, plus the bigger [Suzuki] fork and [its] larger pistons, the stuff passes through and settles at the bottom of the fork so it doesn’t affect damping.”
I watched Bostrom chip away at his lap times and move through the field during Friday’s 50-minute practice. Progress was steady at first: 1:32.143 (Position 9), 1:27.905 (P6), 1:27.736 (P9), 1:27.532 (P9), 1:27.627 (P8), 1:27:397 (P8), 1:26.733 (P6). Then, it slowed: 1:28.954 (P6). 1:28.442 (P8), 1:27.524 (P9). Rockstar Makita Suzuki’s Tommy Hayden topped the session with a 1:24.988).
What was happening? The more Hickson softened the rear suspension by reducing compression damping and dialing out spring preload, the faster Bostrom was able to lap—to a point. The 130 Nm rear spring that had worked well at Mid-Ohio was too stiff for Laguna. Eventually, handling was negatively affected.
“Dropping the back killed the steering,” Bostrom said. “As we loosened up the shock, it got tougher on the brakes.”
Up front, Hickson had replaced the left 10.5 Nm fork spring with a lighter 10.0. He left the right leg at 10.5, effectively creating a 10.25 rate, with six turns of preload on each leg. Of course, while Hickson was dialing in the suspension, crew chief Richard Stanboli was engineering other changes: brakes, gearing, engine mapping, a new rear tire, etc. Each step forward presented new questions.
For the first of the two Saturday qualifying sessions, Hickson came prepared with two setups, one each for the A and B bikes.
A bike:
Fork: 10.0 Nm springs, 6mm preload, oil level 170mm (lowered 10mm), R4 valving (unchanged)
Shock: 120 Nm spring, 8mm preload, C22/R5 damping stack
B bike:
Fork: 10.0 Nm springs, 6mm preload, oil level 170mm, R3 valving
Shock: 120 Nm spring, 8mm preload, C6/R5 damping stack
To help the bike “squat and dig in,” Stanboli lengthened the wheelbase by 15mm.
Bostrom was the first rider onto the track. After briefly sampling both machines, he asked the Attack Performance crew to transfer the B bike’s shock to the A bike. With 23 minutes remaining in the session, well downfield in 18th position (1:29.071), he was back on the track with a soft-compound rear Dunlop.
The changes worked and Bostrom was flying: 1:27.897 (P16), 1:26.328 (P7), 1:26.468 (P7), 1:26.089 (P7), 1:25.866 (P6), 1:25.482 (P4).
Bostrom returned to pit lane. The rear tire had spun 90 degrees on the forged aluminum rear OZ Racing wheel. A second identical wheel, also with a soft tire, was mounted in place of the original. “We need to dimple the rim,” Stanboli growled. After one flying lap (1:26.610), with just 4:30 remaining, Bostrom returned once more to pit lane. Stanboli removed one turn of preload from the fork and took out one click of compression on the shock.
First a 1:27.097 (P6), then—bang!—a 1:25.143 (P5). A newly confident Bostrom completed Q1 just .695 of a second slower than his brother, Ben, who led the session. Progress!
Fresh concerns? Bostrom complained of “dribble”—chatter—at the corner apexes. Hickson once again lowered the oil level, this time from 170mm to 180, for final qualifying. He also took out one click of rebound in the shock. Both A and B bikes were set up identically. Tire choices? Medium front, soft rear.
Once again, Bostrom was the first rider on the racetrack. For most of the session, he was eighth, then seventh. With 14 minutes to go, the single turn of fork preload that had come out during the morning session went back in, along with a new soft rear tire, the second of the session. Bostrom then reeled off two quick laps: a 1:25.698 and a 1:25.079, the latter good for sixth-quickest and the middle of Row 2 between Larry Pegram and Jake Zemke for Sunday’s race. “I think we’re competitive if we’re .2 seconds behind Tommy Hayden,” grinned Stanboli. “What do you think?”
Due to Sunday’s busy on-track schedule, American SuperBike only got an 8-minute warm-up session prior to the race. The sole suspension change was new, slightly firmer valving in the shock: C7/R5 vs. C6/R5, to “work the front more and not squat as much.” Bostrom led the first lap, posting the fifth-quickest time, a 1:27.721. On his fifth lap, Bostrom posted the fourth-quickest time, a 1:25.668.
Bostrom was ecstatic, describing the bike as the “best it’s been all weekend.”
This is how suspension tuning—and many other things in life—really works: You never know how far you can go until you go too far.
