Safe braking at a bike’s maximum potential deceleration, that’s what ABS provides. But how does motorcycle ABS work?
Antilock Braking systems (ABS) provide safe braking at a bike’s
maximum potential deceleration. After decades of development, ABS is
now standard equipment on many bikes, and has been required by law on every motorcycle sold in Europe since 2016. How do they work, though, and why do we need them?
Why It Works
The maximum braking force a wheeled vehicle is able to achieve, called threshold braking, occurs just
prior to wheel lockup. When you get good at threshold braking you’ll
recognize it by the howling noises your tires make. Unfortunately, that
threshold varies by road surface and condition. Weather, surface
temperature, sand or other hazards, and uneven pavement all factor into
the point at which motorcycle tires let go. The grip of the tires
themselves varies by age, type, and condition. The geometry and weight of the motorcycle also plays a part in this complicated equation.
Early ABS systems
weren’t very much of an improvement. They were able to prevent wheels
from locking, but often couldn’t achieve the same rate of deceleration
as a reasonably skilled rider and were prone to kicking in when not
needed. You’ll encounter riders who insist they’re better at braking
than ABS is so they don’t need it, and these are probably the systems
they’re remembering. Thanks to the ever-increasing sophistication of
computerized control units, modern ABS has improved to the point where
its actuation is undetectable and its effectiveness is undeniable.
What Makes It Work
All
ABS systems share the same basic components: a slotted ring on each
wheel is used to monitor and compare wheel speeds, with a microprocessor
in the ABS control unit, or module, making constant calculations. The
rider still actuates the brakes via hydraulic lines. On an ABS-equipped
bike, the hydraulic pressure flows through a pump controlled by that ABS
module which is fitted with simple solenoid valves. These valves have
the ability to open and close very, very quickly, and they have improved
significantly through years of development.
As
technology advances, additional sensors collect more data. Those sensors
can include lean angle, handlebar angle, and throttle position, along
with wheel speed sensors. Each have started informing the other of their
individual actions. As microprocessors get smaller, more powerful, and
less expensive, the motorcycle’s central computer collects information
from the speed sensors, using it in concert with information from the
other sensors to provide things like traction control, launch control, and anti-wheelie control. The sudden proliferation of electronic rider aids
used in modern race bikes, which has now trickled down to a whole bunch
of production motorcycles, started with the humble, early, clunky ABS
module and its wheel speed sensors.
How It Works
You’ve
probably been there, riding at night in the rain, when someone without
the greatest eyesight pulls right into your path. You grab a big ol’
handful of brakes, and stomp on the pedal, and instead of your front
wheel slipping out from under you on that smoothed-out metal manhole
cover, you and the bike come to a perfectly composed, upright stop.
You
remained upright was thanks to the ABS module and its constant
monitoring and comparison of wheel speed, which detected the wheel speed
mismatch, then opened those solenoid valves to release piston pressure
on the brake pads for a fraction of a second, then closed them, then
opened them again, repeating about every hundredth of a second or so,
until wheel speeds matched again, or the bike was at a stop. The only
thing you had to do was mash those brakes, and keep piloting the bike.
ABS Bikes Then And Now
Twenty-plus years ago, bikes equipped with ABS were mostly heavy tourers.
Actuating an older bike’s ABS saw a ton of lever pulsing as the system
modulated brake pressure a few times a second. You could feel the rate
at which it could process data, and there was definitely an “oh shit no
brakes!” moment in there the first time those solenoids let go. While it
prevented wheel lock up, it wasn’t too much better than a really
skilled rider. Add about ten years of development and that pulsing was
instead a vibration, and the stopping distances moved just forward of a
very good rider. And since no rider can predict every situation (like
invisible piles of chip-seal chips on the road), ABS wins every time.
Modern
ABS technology has advanced to undetectability. You and the bike simply
come to a controlled, rapid stop in the shortest distance possible. No
pulsing, no second-guessing the efficacy; the bike is held at threshold
braking no matter the surface, until you release the lever. Not only is
it seamless, but current ABS delivers all the feel and control you get
from a non-ABS bike. On the latest generation of ADV and dual-sport
bikes, you can still sometimes catch ABS off-guard while attempting to
shed speed on a steep descent, where you actually want full rear brake
lock.
You Definitely Want ABS
Modern ABS
systems doesn’t take control or feel away from the ride. Even the most
skilled racers can no longer out-brake the computer, even in perfect
conditions. In today’s horrifying smartphone-distracted traffic, ABS is a
great tool in your line of defense against careless, distracted
drivers. Your ABS bike simply stops faster and more safely. That’s an
advantage you need, whether you want to admit it or not.
