4 THINGS YOU NEED TO KNOW

Motorcycle News (UK) - - Garage -

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.

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