How Does Motorcycle ABS Work?


Category: Technology

The Process

There you are, riding along in the rain when — without warning and despite having a clear line of site to you — Nathan No Look pulls out in front of you at the last possible second. You grab a big handful of front lever and stomp on the back, slowing to a controlled halt as Nate continues his Twitter battle with sports fans from the rival team.

The reason you didn’t plow through his door and temporarily force him to look up from his phone was because the ABS ECU, during its constant monitoring and comparison of both wheel speeds, determined that a lock up was imminent and opened the pump’s valves to release pressure on the calipers, then modified the degree of pressure reaching them every hundredth of a second or so to optimally take advantage of what traction was available and hold you at a rate of deceleration just this side of wheel lock up. All you did was hang on to the levers and try not to urinate on yourself.

By comparing wheel speeds and the rate of change for each, the ABS ECU is able to effectively determine how hard it can allow the brakes to actuate, even without knowing what’s going on between the tires and the road surface.

Different Scenarios

That same basic function is what happens with any type of ABS. Some bikes add in brake linking, where hitting the front or rear lever may proportion some brake pressure to the other end, while others include an “off-road” mode designed to better work in low traction environments where some wheel lock is desirable.  But, all that is taking place in the ECU’s electronic brain, not through a different mechanical spec or different actuation methods.

Big Data

The reason ABS has become so extraordinarily effective is that it now benefits not only from vastly more data informing its actuation, but also with a greater capacity to quickly process that increased amount of data. The actual mechanical components of ABS remain virtually the same, but they do get smaller and lighter and better able to actuate quickly and finely thanks to advances in materials and production processes. The latest ABS systems add only 4.5 lbs to a bike’s weight, down from 10 lbs or more in the 1990s.

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