In 1976, Ron Pierce was riding my Kawasaki KR750, which was a purpose-built water-cooled roadrace design—that is, sharing no parts with the production 748cc H2. After one event, I found that brake heat had melted all the grease out of the rear-wheel bearing on the brake disc side, a problem I had to fix. Nobody wants to contemplate a wheel-bearing seizure.
I saw that Ron was using a lot of rear brake, enough to go through normal brake pads really quickly. Accordingly I ordered Ferodo’s hard pad of that time, DS11. The disc was a cast-iron “hat section” combined disc and carrier, normally bolted to the face of the right-hand wheel-bearing carrier. I arranged to put an air gap between them to stop most of the heat that had been flowing into the bearing.
On other occasions, Ron had referred to the practice of many national numbers—his was 97—of supplementing income by riding the many regional dirt-track events within acceptable driving distance. Often, he related, he could ride Wednesday evenings and weekends and pick up $300 or so if things went well.
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The problem of grease melted out of that bearing made me understand what Ron was doing. He was using the rear brake to moderate the sudden torque rush of that piston-port 750 so he could accelerate off turns without the upset of slide-outs caused by wheelspin. Why not control that with the throttle? Because varying pressure on the rear brake pedal acted much faster than ponderously winching the throttles up and down like the sluice gates on a hydroelectric dam.
Attend any American Flat Track race and walk through the paddock. Why do those bikes have those great big car-sized brake discs on their rear wheels? As the program grinds through the heats, the sun goes down and darkness creeps across the proceedings. A line forms under the yellow lights at the concession. Burgers, fries, and Cokes fuel the people, and Sunoco fuels the bikes.
As it grows dark, you begin to understand those big discs. Being used as they are as traction control, they are glowing visibly red. Here comes a rider into turn 1 with a shower of sparks streaming from the rear caliper; continually absorbing unwanted engine power lap after lap has raised the brake temperature to a level at which such pyrotechnics begin.
When electronic rider aids began to appear, first on European bikes and then on Japanese product, old-timers croaked out objections. Manufacturers were trying to turn courageous riders into gutless capons! Rip out the electronics and man up! But just as in dirt track and roadracing four decades ago, people were seeking to control traction to go faster by whatever means were available. AFT has a 40-pound maximum weight limit for rear wheels precisely because, otherwise, builders will inflate tires with water instead of air or otherwise add wheel mass to act as flywheel to suppress wheelspin. The act of suppressing wheelspin, however you implement it, is traction control.
Why have the “man-up” complainers faded out? The easy theory is that the reaper has called those oldsters away from the scene. But my personal belief is that when they finally tried “rain mode” and other new features they were secretly so pleased to feel like better riders that they just enjoyed riding and said no more.
In our next test at Loudon, New Hampshire, Ron Pierce showed that the KR750’s wheel bearings were now running merely warm. The smell of burning pot handles told me that DS11 friction material was doing its job, and when the bike came in from its final exit, I could see a dull glow from the disc.
