This modern wizardry helps to keep your bike upright, and you off the pavement.

Rider assist systems like ABS and traction control have become almost universal in motorcycles. ABS itself has been around for almost four decades. It was first introduced into motorcycling way back in 1988, on the BMW K100RS. I remember having ridden that bike back then, and testing the rather rudimentary (by today’s standards) system in a back alley. 

The system monitored road speed and wheel rotation and activated when either wheel spun slower than the indicated road speed. It cycled several times a second (ABS now cycles in milliseconds), locking either wheel for a fraction of a second, releasing brake pressure to avoid full lock up, and then repeating that cycle until the bike came to a stop. 

It was a slightly terrifying and noisy experience, actually, as the tires chirped intermittently and the fork bobbed up and down, bouncing repeatedly off its bump stops. It was meant to help avoid a crash while braking hard only in a straight line, as the momentary lockup of the front wheel would definitely force an unfortunate meeting of rider and pavement when leaned over in a turn.

Traction control is a much more recent arrival in motorcycles. The first bike to feature TC (not a rudimentary ignition-retarding system, but true traction control managed by the ECU) was the Ducati 1098R in 2008. I had ridden that bike on a racetrack, and it was my first experience with traction control.

The system monitored wheel speeds, and intervened when it sensed that the rear wheel was spinning faster than the front, whether due to wheel spin or a wheelie. Since the bike lacked ride-by-wire throttle control (that was introduced in the Yamaha R6 in 2006), the ECU managed ignition timing, spark control and fuel delivery to reduce power when it sensed rear wheel slip, causing the engine to sputter when the TC engaged. Since the system lacked an inertial measurement unit (IMU), it wasn’t precise enough to alter the level of intervention while leaned over in a turn.

Ah, the IMU. The first time this piece of electronic sorcery appeared on a motorcycle was in the 2011 Aprilia RSV4, and it has greatly refined the operation of both ABS and traction control. According to Bosch, a leading manufacturer of IMU units, “The inertial measurement unit measures up to six dimensions: yaw, roll and pitch rate as well as lateral, longitudinal and vertical accelerations.” 

What this means in practical terms is it measures acceleration from a steady state forward and rearward, side to side, and up and down, as well as angular velocity on three axes — fore and aft pitch when braking and accelerating; right and left roll when leaning; and right and left yaw off a centreline when changing direction. All of these parameters are critical, since each one has an effect on traction; combine several of these factors and traction can be greatly compromised. 

The IMU does not do any thinking or gathering of information but rather relays data in real time to the ECU. A six-axis IMU like the one described above does this with two main sensors, called MEMS (micro electromechanical systems). 

One is an accelerometer, which utilizes fixed and moveable sensing arms to measure any movement from a standing state. These microscopic arms resemble a pair of combs with their tines intertwined. The moveable arms work against a spring; any movement fore and aft causes the moveable arms to move within the fixed arms. As the distance between the tines changes, so does the electrical capacitance between the gaps, which is processed by the IMU and sent as a signal to the ECU. The accelerometer measures lateral, longitudinal and vertical accelerations. 

The second is a gyroscope, though it is not a conventional type that uses a spinning mass but rather one that utilizes a mass that vibrates at a fixed rate. Physics dictates that a mass will vibrate on a single plane; when the gyro unit rotates, it senses changes in the direction of this vibration, which is again processed by the IMU and sent as a signal to the ECU.

The ECU doesn’t do any thinking either; it gathers the data from the IMU, as well as road speed, individual wheel speed, engine speed, throttle position, gear position, and brake pressure data, and compares it to preprogrammed 3D maps to manage the throttle or ABS. So, regardless of how much you open the throttle or hit the brakes in a turn (within reason, of course), the ECU will only open the throttle or modulate brake pressure at a certain rate, based on the data gathered through all the sensors plugged into the system. 

Adjustable ABS and throttle control means that more than one preprogrammed map is available, thus altering the threshold of each. Of course, programming the ECU is a complex operation involving hundreds of thousands of kilometres of testing in a multitude of conditions. But the outcome is motorcycles that are easier and safer to ride.