This Mark Wernham photograph of Nicky Hayden braking at Silverstone is dramatic but also counterproductive. What’s important is what BMW factory rider Leon Haslam told me at Miller Motorsports Park this past May during the World Superbike race weekend: “If rear braking is lost, the rear will rise and overall braking will suffer.”
We can find out the brake torque required to lift the rear wheel by measuring the wheelbase and multiplying it times the weight on the rear tire. The rear tire lifts when braking force, multiplied times the overall center-of-gravity height, equals rear-wheel load multiplied times wheelbase.
What Haslam was talking about is that for maximum braking, cg height must be reduced to as small a value as possible. That happens at the front, naturally, as brake dive. At the rear, the brake caliper is intentionally attached to the swingarm so that brake torque also compresses the rear suspension somewhat, further reducing cg height. What Haslam means is that if the rear brake ceases to compress the rear suspension, the back of the bike will rise, raising cg height slightly, and forcing the rider to reduce front braking to keep the rear of the bike from rising farther. Each rise of the rear raises the cg height in a vicious circle that can ruin one’s whole corner approach.
The first time I saw controlled braking with the rear wheel off the pavement was at Loudon in 1976, when Gary Nixon approached Turn 10 every lap with the rear tire 3 inches up. When I asked him about this years later, he said, “I didn’t have any idea I was doin’ that at the time, but a lot of people have asked me about it.”
The Kawasaki KR750 that Nixon was riding that year had the first Teflon-bushing Kayaba fork. The following year, Nixon rode a Yamaha TZ750 with an old-technology (aluminum on steel) Kayaba. The back tire would come up, but the motion was jerky—no longer smooth enough to be controllable.
Mark’s photo of Hayden makes me wonder if MotoGP bikes apply something like their anti-wheelie software to the “stoppie” problem. Here, it looks like the answer is no.