How Harley-Davidson ABS Brakes Work

ABS braking systems are now standard on medium- and large-displacement motorcycles. We'll try to explain what they consist of and the advantages that are making them popular even among less sporty models, such as custom bikes.

ABS stands for "Anti-Lock Braking System," and was designed in 1929 for aircraft brakes. Its principle is to prevent the wheels from locking up during braking, preventing the tires from skidding uncontrollably on the road and losing grip, thereby achieving maximum friction (and therefore braking) capacity while simultaneously maintaining balance and steering.

Components and operation
We'll now discuss the components that make up a motorcycle's ABS system and how they work. Although there may be slight variations depending on the make and model, the principles are the same.
The system starts with a conventional brake pump and caliper, to which a hydraulic unit is attached in the conduit that connects them, allowing braking pressure to be maintained, released, and recovered while the brake lever or pedal is pressed.

This Hydraulic Unit is electronically controlled by the ECU or ABS control unit.

At the same time, sensors are installed that control the rotation speed of the wheels and can measure holes in the brake disc as it rotates,

or read magnetically coded bearings , as in Harley-Davidson ABS systems.

The ABS ECU therefore knows the speed at which each wheel is rotating. If one stops more quickly than advisable (locking and possibly skidding), a signal is sent to the Hydraulic Unit to release pressure (even if the driver continues to apply the brake) until the wheel rotates slightly again, at which point pressure is restored to continue braking.

If the possibility of skidding persists, the process is repeated. All of this happens at a rate of 7 times per second, so it's barely noticeable to the driver, who simply notices a vibration or pulsation in the brake lever or pedal.

Decisions about whether or not to activate the system (this is known as an “ABS Event”) are made by the ECU based on programmed values, comparing them with data from the wheel rotation sensors.

Advantages and limitations of ABS
With this complex and effective system, the rider can stop the motorcycle in the shortest possible time, without having to worry about the wheels locking and skidding. At the same time, by maintaining traction, we can maintain balance and steering.
Therefore, its effectiveness will be most noticeable on slippery surfaces (gravel, ice, poor pavement, etc.) and when operated by inexperienced drivers. It's worth noting that all studies show that even professional drivers achieve shorter braking times with the ABS system.
This means that in an emergency braking situation, ABS significantly increases safety and effectiveness.
It's important to keep in mind that ABS isn't suitable for all driving situations. Its effectiveness is minimal when turning the handlebars sharply or cornering, so you should continue to take normal braking and driving precautions.
In the event of emergency braking, you must keep the engine upright and straight (this is essential) and brake firmly with both brakes, without releasing pressure. The ABS will do the rest of the work for you.

ABS failures
Many users remain skeptical of electronic control systems, especially those that affect safety, as they can fail due to vibration, humidity, poor contacts, etc.
In the case of ABS, we can say that it is a completely safe system, since the ECU continuously monitors the status of the sensors and components, and if it detects any anomaly, the system "disconnects," turning on a fault warning light on the instrument panel.

In no case will we be left without brakes, since when the ABS stops working, we simply have a traditional braking system, without anti-lock braking.
TECH TIP: On some models, the ECU compares the readings from the front and rear wheel sensors, so prolonged wheelie activity with the front wheel or burnout with the rear wheel can create a false ABS error.
One last recommendation: don't wait for a difficult situation to test your ABS. Practice emergency braking in a safe environment to familiarize yourself with the controls and braking capabilities. This way, driving will be more intuitive, fun, and safer.

Frank Burguera

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