2010 Buell 1125CR: Getting a handle on track-ready tuning
FLAIR PHOTOGRAPHY
Tuning the Buell 1125CR’s suspension allowed Steve Bond to corner like this.
Harley's decision this week to close Buell was a shock to many in the industry. Even though the early Buells were rather like an unfinished high school project, lately the company had been making some very nice motorcycles.
I'm especially fond of the Ulysses models, and the XT model with standard bags and 17-inch wheels went on my list of "motorcycles I'd actually consider buying."
The 1125R was Buell's latest assault on the world's best sportbikes and was armed with a liquid-cooled, Rotax-built, V-twin and a totally new chassis. I had a chance to try out the CR version of the 1125 in July.
Riding sportbikes on the street, I usually complain about the narrow focus and extreme riding position, but with the Buell I booked a Pro 6 track day at Mosport (www.pro6cycle.com), which is really a sportbike's natural habitat.
As an added bonus, John Sharrard of Accelerated Technologies (www.acceltechracing.com) offered to help me dial in the Buell's suspension to fully explore its potential.
When the date approached, the 1125R wasn't available but distributor Deeley's had a new 1125CR so I took that instead.
The "CR" designation stands for Café Racer, a term coined by the Brits in the 1960s when they fitted low or "clubman" bars on Triumphs and BSAs and "raced" from one coffee shop to another.
The CR has a small flyscreen rather than a full fairing and the large lobster-claw air scoops flank the "furrowed brow" single piece headlight, giving the CR a somewhat menacing Darth Vader-ish appearance – especially in black.
To prep the bike, I replaced the anti-freeze with water and taped over all lights. The Buell's front turn signals are integral with the mirrors and requires dismantling the motorcycle to find the wiring connectors. So I just left the mirrors on and taped over the glass.
The first session with the factory suspension settings showed how a bike that handled reasonably well on the street became almost unrideable on the track.
Even with judicious trail-braking (keeping a bit of brake entering the corner), the CR didn't want to turn and, once into the corner it was a struggle to keep it there. When power was applied, it wanted to understeer right off the pavement. And, when tapped out in sixth gear on Mosport's long, uphill backstraight, the CR started a slow weaving which, although not dangerous, certainly got my attention.
Sharrard took some measurements to establish baseline settings on the suspension.
We lifted the back wheel completely off the ground and measured between the axle and the bottom of the tailpiece.
I climbed aboard and the measurement was repeated. The difference between the two is rear sag. For racing or track use, rear sag should be somewhere around 25 mm. For street use it should be 30 to 35 mm. The Buell's was 54 mm or way too soft. If the rear is too soft, the front forks extend, causing the handling problems I experienced.
Once the seat was removed, the adjusters were exposed and Sharrard dialed in the required 25 mm of rear sag. Note that adjusting preload does not stiffen the spring, it merely shortens or extends the length of the spring.
Once sag is set, damping can be addressed.
Compression damping is the rate at which the wheel reacts to bumps. If the damping is too soft, the bike will wallow and if too hard, it will bounce. Rebound damping controls the rate that the wheel will extend. Mosport is very bumpy, and if the fork is slow to rebound, it will just keep compressing until there's no suspension travel left.
With the sag set, Sharrard attached a zip tie to the fork tubes, which measures suspension travel as the forks compress. With a feel developed by years of experience both as a tuner and nationally ranked Pro road racer, Sharrard then set damping baselines and sent me on my way.
Immediately, I noticed improvement as the Buell was no longer reluctant to turn and once there, it stayed put. It still had a bit of understeer when power was applied but it was a huge improvement.
It was still weaving at top speed however, and with the bike cornering better and my increasing confidence, the digital speedometer was showing 235-240 km/h on the straight. Gulp!
The Buell's eight-piston caliper with huge, rim-mounted disc had a soft initial bite and a somewhat vague feel, making trail-braking a bit of an adventure. I started braking earlier and gentler, which seemed to work.
The zip tie showed the forks were almost bottoming so we cranked in one turn of preload and a couple of clicks of compression damping. The handling improved once again, and I was able to go faster.
And that's the double-edged sword of suspension sorting. Adjustments make the bike better, enabling you to push the bike harder, which requires more adjustment to bring the bike up to snuff again.
Eventually, we ran out of adjustment and the zip tie was still almost bottoming, indicating that a rider of my skill level and (ahem) weight would require a heavier spring.
We couldn't, however, tune out the weaving.
Sharrard figures the mirrors and "lobster claw" side scoops were causing the high-speed instability – just a matter of aerodynamics. Or lack thereof.
Sharrad told me that when dirt trackers experience the same weaving, they take their left hand from the bars and grab the fork tube by the steering head.
Gulp. During the final session, with the speedo indicating 247 km/h, I casually removed my hand from the left grip and grabbed the fork tube.
The weaving stopped and the Buell was rock solid.
It was a real eye-opener how an initially ill-handling motorcycle can be transformed through simple adjustment. Sharrard's service is available at all Pro 6 Cycle trackdays and Shannonville regional races.
stevebond8@yahoo.ca Share your thoughts with other Wheels readers at wheels@thestar.ca
Woman's win over Honda opens door to mileage claim free-for-all
Video: Chevrolet Sonic a small car with a big car price
