Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126944
sensor that is similar in principle to an electronic ignition. A gear with 100 teeth is attached to the brake rotor, and an pickup mounted just above it sends a pulse to the system's computer as each tooth passes. The system' computer then evaluates the rate of change in the freq uency of the pulses. If that change is very rapid, indicating wheel locking instead of controlled deceleration, the computer activates the pressure modulator, reducing hydraulic pressure in the wheel cylinder until the wheel unlocks. The cycle is repeated up to seven times per second, as long as the rider is applying sullicient pressure to lock the brakes. During the BMW demonstration, it was clear that the system was cycling considerably slower than seven times per second, but the BMW engineer present explained that the system slows down as the surface gets more slippery. It also does not operate below 2.5 mph, but that didn't seem to faze the test riders, perhaps since it takes only a few inches to stop from that speed. Each wheel's decelera tion i eva 1uated independently, except that the front wheel's speed is considered by the computer in determining whether the rear brake is locking, in order to distinguish between brake locking and say, a jerky downshift. In order to provide the system with a safety reserve, each wheel sensor has two sets of wires leading to the system's computer. While one set is active, the other is being checked, and the two alternate every 10 seconds. If there is a failure, a red light £lashes on the motorcycle's dashboard, indicating that the rider can no longer rely on the ABS system. The 8.4-pound pressure modulator sits above the footpegs. The basic architecture of the system consists of two wheel sensors, two electric-motor pressure modulators, one electronic control unit, and a warning light. The heaviest pan of the system is the pressure modulators, which weigh 8.4 pounds each, but are mounted near the footpegs for the least possible effect on handling. Perhaps the biggest disadvantage of the ABS system is not weight or complexity, but price. BMW expects to offer the system as an option on the KIOORS, RT, and LT next fall for approximately $1000. That may explain why other manufacturers have been reluctant to o(fer similar systems. Spokesmen for Honda, Suzuki and Yamaha would not comment on whether or not their companies were planning to o(fer ABS on motorcycles. Kawasaki's Mel Moore, however, said that his company is studying different systems, and is very interested in ABS, partly because the increase in safety mIght make motorcycling m?re appealing to buyers. The complete anti-lock brake system; wheel sensors, pressure modulators, the electronic control unit and a warning light. . But he also said that company engineers are concerned with rider compatibility with ABS 'and . non-ABS brake systems. o for the time being, BMW is alone in its announcement of an AB braking system. Buyers of what are already exclusive machines can opt for an even greater degree of uniqueness by ordering the AB sy tern next £all. Arid when questioned, BMW spokesmen did not rule out the possibility of ABS being retrofitted to earlier models, which would be a boon to current BMW owners. For the journali ts assembled at BMW's demonstration, however, there was one big disappointment. Nobody got to try either the ABS-equipped KIOORT, or the outrigger-equipped machine. So for now, all information about the system i~ second-hand, although BMW has clearly proved that it works. The next step is for BMW to produce the system, and give motorcyclists a long-awaited helping hand.. Hydraulic circuits Electrical circuits 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Hand brake lever Brake master cylinder, front Sensor, front Speed impulse generator, front Pressure modulator, front wheel Foot brake lever arake master cyclinder. rear Pressure modular. rear wheel Sensor. rear Speed impulse generator, rear ABS electronic control unit Battery Ignition switch Cancellation button ABS warning light ABS safety relay 16 12 ®®®®®® 13