Some riders consider ABS to be a sign of weakness, an unnecessary device for rookies or grandpas. The tough guy philosophy is often something like, “I can brake better without it.”
Guest writer Lou Peck shares his knowledge about Anti-lock braking systems.
I recently stepped into a SoCal dealership looking for an ABS-equipped motorcycle and the salesman tried to convince me that “ABS doesn’t really do anything unless it’s wet, or you’re on dirt,” and “you don’t need ABS on a light bike.” Several knowledgeable riders in my own community also thought ABS was useless. That’s when I realized most riders just don’t know how and why ABS can help…and that needs to change.
As a forensic engineer, I’ve reconstructed hundreds of motorcycle collisions and have a bit of a different perspective on the topic. I’m hired to figure out how a collision occurred and if it could have been avoided. I’m typically tasked with figuring out speeds of the involved vehicles, vehicle locations, and timing. The photo below shows what I usually see when I investigate motorcycle crashes.
Notice the skid mark from the rear tire of the motorcycle. My colleagues and I see evidence of a skid from a locked rear brake in most cases we work. The famous Hurt Report found that only 22% of riders braked appropriately when faced with a hazard, stating that “most riders would overbrake and skid the rear wheel, and underbrake the front wheel greatly reducing collision avoidance deceleration” . Not good.
How does ABS Work?
The amount of stopping force a tire can generate is related to how much it’s slipping, as opposed to simply rolling. Most people don’t know that optimum traction occurs when the tire is slipping at a rate of something like 15%. Above or below that and you’re not getting max grip for stopping.
When tire slip approaches about 20%, ABS automatically releases the brakes a bit and then quickly reapplies. That’s the pulsing vibration you feel at the brake lever or pedal. This releasing and reapplying occurs several times per second, keeping the tire slip in the range shown in the graph.
ABS is Better Than You
Since ABS operates in a range surrounding the peak but not constantly at the peak, professional test riders can often come to a stop in a shorter distance with ABS disabled. Mr. Tough Guy probably heard this and his ego insists he can out-brake an ABS system. The truth is that the vast majority of riders do not have the skills of a test rider. It turns out most riders can only brake at about 60% of the bike’s capability, compared with nearly 100% for test riders.
The Heat of Battle
And performing an optimal braking maneuver on a test track without the threat of an impending collision is a lot easier than trying to perform a flawless emergency braking maneuver on the street. If you don’t get the bike stopped in time you’re in big trouble.
Skidding is Bad
A skidding tire makes matters much, much worse. When a tire slip approaches 100% (lock-up), stopping power is reduced by about 20%. Not only does skidding reduce stopping power, it also reduces lateral stability of the tire and with no grip to spare, the tire will slide left or right. For the rear, this means it might step out to the side causing the motorcycle to rotate, sometimes to the point where it just rotates and rolls all the way to the ground in a lowside fall. Locking the front results in the motorcycle almost immediately hitting the deck. Not a good evasive tactic.
You’re Not as Good as You Think
Most riders can only exploit 60% of the bike’s stopping power, and that probably includes you. Below are six solid studies showing the average rider can only hit a deceleration rate of 0.64 g’s when most bikes are capable of about 1.0 g [2-7]. Those studies analyzed 1,200+ braking tests, from over 600 different riders, conducted in controlled environments with no threat of injury or death and no uncertainty of the appropriate response (do I brake, swerve, accelerate, etc.). Even in this controlled environment, locking occurred often .
ABS is Your Friend
So, what happens when we introduce ABS? Some smart guy named Vavryn investigated the behavior of 181 riders during 800 tests . The riders performed two tests on their own non-ABS motorcycle, and then two on an ABS-equipped motorcycle. The average braking rate for motorcyclists on their own motorcycle was 0.67 g’s. However, when riding the motorcycles equipped with ABS, that number jumped up to 0.80 g’s, nearly 20% improvement despite riding an unfamiliar machine. Overall, 85% of the subjects improved braking with the ABS motorcycles, and the novice riders achieved ABS-braking rates almost equal to experienced riders.
The Difference Between Whew and Ouch
What’s the difference between braking at 0.80 g’s compared to 0.64 g’s? Say you’re going 50 mph, brake at 0.80 g’s and are just barely able to avoid hitting a left-turner because you’re riding an ABS-equipped bike. Now, let’s say you’re in the same situation, but only brake at 0.64 g’s…you’ll hit at over 20 mph. Ouch!
In 2013, the Insurance Institute for Highway Safety published an in-depth study of over 425,000 motorcycle insurance claims that directly shows the benefit of ABS . It turns out that motorcycles equipped with ABS saw a 20% reduction in collision frequency (those equipped with ABS and a combined braking system saw a massive 31% reduction). Relative to fatal motorcycle collisions, ABS alone was associated with a 31% reduction !
I used to be an expert racer with a tight and technical home-track that required a lot of hard braking, and I got pretty good at it. However, after seeing what I’ve seen in my line of work, I don’t fully trust myself to fully exploit the motorcycle’s ability when presented with a life-threatening hazard. Fortunately, ABS is there to ensure I don’t lock a tire and lose control and reduce my chances of being involved in a collision. That’s why I own a street-bike with ABS, and I highly recommend you do the same.
Lou Peck is a Forensic Engineer based out of Southern California. Lou has authored many peer-reviewed technical publications in the field of motorcycle collision reconstruction and regularly testifies as an expert witness. Lou is a former roadracer and track day instructor.
 Hurt, H.,Ouellet, J., and Thom, D., “Motorcycle Accident Cause Factors and Identification of Countermeasures, Volume 1: Technical report,” Traffic Safety Center, University of Southern California, 1981.
 Hugemann, W., Lange, F., “Braking Performance of Motorcyclists,” 1993.
 Ecker, H., Wasserman, J., Hauer, G., et al., “Braking Deceleration of Motorcycle Riders,” International Motorcycle Safety Conference, Orlando, 2001.
 Vavryn, K., Winkelbauer, M., “Braking Performance of Experienced and Novice Motorcycle Riders – Results of a Field Study,” International Conference on Traffic & Transport Psychology, 2004.
 Bartlett, W., Greear C., “Braking Rates for Students in a Motorcycle Training Program,” Accident Reconstruction Journal, Vol. 20(6), pp. 19-20, 2010.
 Muttart, J., Fisher, D., Kauderer, C., et al, “Influence of Riding Experience on Glance Behavior, Brake Response Time and Deceleration Rates by Drivers and Motorcyclists,” Proceedings of the Sixth International Driving Symposium on Human Factors in Driver Assessment, Training, and Vehicle Design, Lake Tahoe, CA, 2011.
 Dunn, A., Dorohoff, M., Bayan, F., et al, “Analysis of Motorcycle Braking Performance and Associated Braking Marks,” SAE Technical Paper 2012-01-0610, 2012.
 Insurance Institute for Highway Safety Bulletin, “Evaluation of Motorcycle Anitlock Braking Systems, Alone and in Conjunction with Combined Control Braking Systems,” Vol. 30, No. 10, April 2013.
 Teoh, E., “Effects of Antilock Braking Systems on Motorcycle Fatal Crash Rates: An Update,” Insurance Institute for Highway Safety, 2013.
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