4 THINGS YOU NEED TO KNOW
1 Give me a ring
The ‘toothed’ ring bolted to each wheel is called a phonic ring. There need to be enough teeth to give enough info but without overloading the sensor. It would be hard to smoothly detect wheel lock-up with just two teeth as that’s only one pulse per half wheel revolution. Most phonic rings use 60-70 pulses.
Electronic brain 2
Your cornering ABS needs to know when your bike is leaning. The IMU (Inertial Measurement Unit) helps the system to establish this by measuring the chassis’ attitude (roll and pitch). But it isn’t the IMU itself that makes the system work, it only provides an input to control systems that take advantage of it.
3 Wheel sensors
Variable reluctance ( VR) type sensors were used historically – with two wires and outputting an AC voltage that changed in frequency and amplitude with speed. They are very reliable but don’t work well at low speed so active sensors are now used. These are ‘powered’ and output a signal that works down to zero speed.
Pump it up 4
The hydraulic control unit is the heart of your bike’s ABS system. It normally uses an electric motor to generate pressure, an accumulator and a series of electrically controlled valves to modulate the pressure in the brake lines. Some systems also distribute the pressure between front and rear brakes. From a rider’s point of view, it’s important that the system reacts smoothly most of the time, but in an emergency, this doesn’t matter as long as the system works and prevents an accident.