Staying alive Kevin Williams on ABS – how it works and why to trust it
Articles on braking virtually always focus on conventional motorcycle brakes; ie, those where the front brakes are operated by the handlebar brake lever independently of the rear brake which works from the foot brake lever. And truth be told, until recently our own training has also revolved around the use of conventional brakes for the simple reason that relatively few trainees turned up on machines that had anything other than conventional brakes. But all that is steadily changing, and more and more machines are now fitted with more complex braking systems, and my training has had to move with the times and take notice, and we’re also long overdue a rewrite of the basics of braking to take into account the new technologies.
Anti-lock brakes do what they say on the tin. They prevent either or both wheels from locking during brake application. Sensors monitor the rate of wheel rotation and the ABS unit then uses that information to adjust the pressure of the brake fluid to keep the wheels rotating, and thus preventing skids which can cause loss of control. The original BMW system was based largely on existing car technology. Heavy and relatively crude, it produced strange noises and rather disconcerting power pulses at the lever when it kicked in. And though it kept the wheels turning, the crude on/off nature of the pulses meant it wasn’t particularly efficient in terms of stopping distance. Motorcycle magazines took great delight in showing how their own test riders could out-brake the factory system, even in wet conditions. I seem to recall both the late John Robinson and superbike racer Jamie Whitham comprehensively beating the ABS on a wet braking test.
The lesson that most riders took away, myself included at the time, was the wrong one. They didn't see that it took an experienced expert rider to beat ABS so much as they simply saw that conventional brakes could beat it. About the only exceptions
to the rule were BMW owners. By the end of 1995,
approximately 60,000 had taken delivery of machines fitted with the first generation of ABS technology.
But the technology continued to develop. Feel in use improved, braking efficiency increased and weight came down, and it ceased to be fitted exclusively to high end machines so more and more
‘ ABS allows the rider far better braking control on slippery
surfaces and allows a rider to brake to the limit of
adhesion in an emergency’
of us are now riding ABS- equipped machines. So what does it offer? The big plus is that ABS allows the rider far better braking control on slippery surfaces, and allows a rider to brake to the limit of adhesion in an emergency. This is particularly crucial in our first days on the road or when a rider is getting used to a different machine. ABS has an obvious benefit here. New riders who might overbrake or underbrake can be trained to use the technology to take the uncertainty out of braking, rather than be afraid of what non-ABS brakes might do when used hard. Studies also show that similar overbraking / underbraking accidents happen to experienced riders when they are on an unfamiliar machine. It takes us time to get used to the brakes and tyres on a machine we’ve not ridden before.
Years ago when I was training as an instructor, I tried a hard stop on a Honda Express moped. The front locked instantly and I barely recovered control. I learned later that the instructor I was replacing had broken his arm the previous week performing the very same exercise. I hadn't thought out the front/rear weight balance before I applied the front brake. ABS would have saved myself and the other instructor, and will save many another unwary rider on an unfamiliar machine.
But even for an experienced rider on a machine they know well, there’s a benefit. We know that the road surface can be extremely variable and so even for a skilled rider the big risk in hard braking is locking the front wheel. As a result we’re extremely reluctant to apply anything like maximum force even under coaching conditions, let alone on the road. Accident studies suggest that many experienced riders don't get much past 60% of the available force from the front brake when braking in an emergency. So how do we use ABS? The answer is if we have ABS on conventional non-linked brakes, we make all the same judgement calls about how and where to brake and then brake just like we do with non-ABS conventional brakes. It’s as simple as that...
...with two provisos.
The first is that it’s really important we get out there and actively test the brakes to the point of locking up in a safe area, first at low speed then at steadily higher speeds, and then on slippery surfaces. That way we firstly get the feel for the system kicking in and know what’s happening.
The second is that we don’t make the mistake of releasing the lever when the system DOES kick in. Why? Well, for experienced riders like myself who’ve grown up with conventional brakes, it’s really difficult to overcome those two things. First of all, there’s a built-in resistance to braking to
the limit of adhesion and the point of locking the wheels. Secondly, we have to get used to the idea that the ABS working in an emergency is NOT a sign we’ve made a braking error as it would be on a conventionally braked machine - it means we are braking as hard as we are able to. So actively engaging the ABS is something we should practice, so we are not shocked when it does activate and make the mistake of letting go of the brakes when it kicks in for real on the road.
ABS has come a long way since the crude systems of 30 years ago and we really should trust it to help us to stay upright and under control in an emergency!
Kevin Williams
(c) Survival Skills Rider Training 2013
Post test training for everyone from newbie to experienced with a BTEC qualified professional instructor.
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