After having a few kids and retiring from roadracing several years ago, I recently decided to get back to riding. On the hunt for an ABS-equipped motorcycle that could pull track and street duty, I met some unexpected resistance against ABS (anti-lock braking systems). Don’t get me wrong, I’ve been part of the community long enough to know that some riders consider ABS to be a sign of weakness, an unnecessary device for rooks or grandpas. The tough guy retort is often something like, “I can brake better without it. Leave that junk off my bike.”

That wasn’t what caught me off guard though. It was when I stepped into a dealer here in Southern California and the salesman (who many newbs entrust to point them to an appropriate bike) told 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.” It was also when I spoke to skilled and knowledgeable riders in my motorcycling community who didn’t think ABS could help them avoid a collision. That’s when I realized most riders just don’t know how and why ABS can help…and that’s got to change.

I have a bit of a different perspective on this topic. I’m a forensic engineer and make my living reconstructing motorcycle collisions. People hire me to figure out how a collision occurred, and if it could have been avoided. I’m generally tasked with figuring out speeds of the involved vehicles, and where everybody was and when. This is accomplished by analyzing tire marks, gouges, debris, damage to the involved vehicles, “black box” data, testimony, etc. In addition to reconstructing hundreds of motorcycle collisions, I’ve conducted and published several studies analyzing the behaviors of riders, including their braking performance. Anyway, you want to know what I usually see when I investigate motorcycle crashes?

Take a look at the collision scene photo here. See that thin, dark mark in the bottom of the photo? That’s a skid mark from the rear tire of the motorcycle, and if you look closely enough, you can see a more subtle mark from the front tire. Tragically, this rider didn’t survive the crash. Locking a tire before impact isn’t an oddity, it doesn’t happen once in a while, I see this in most cases I work, and so do my colleagues. Don’t take my word for it though. The famous Hurt Report [1] concluded 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. Way back in 1981 Hurt and his team recommended that the benefits of linked and ABS braking systems be investigated. Surely, because he thought they could help.

Let’s talk a little bit about what ABS does. The amount of stopping force a tire can generate is related to how much it’s slipping, as opposed to simply rolling. Peak stopping force, or deceleration, is reached when the tire is slipping at a rate of something like 15%. Above or below that and you’re not getting max stopping power.

With the assistance of wheel speed sensors, ABS automatically releases the brakes a bit when slip approaches about 20%, and then quickly reapplies them. This occurs several times per second, keeping the tire slip in the range shown above. Since ABS operates in a range surrounding the peak, but is not constantly at the peak, test riders can often come to a stop in a shorter distance with the ABS system disabled. This further encourages our Tough Guy to forego buying an ABS-equipped motorcycle, because he thinks he can out-brake an ABS system on his own. Firstly, I doubt that’s true for the vast majority of riders. You’re not a test rider, and you probably don’t possess the same braking skills. On top of that, performing an optimal braking maneuver on a test track when you have several attempts to do so, and there is no impending collision, is a completely different animal than the circumstances surrounding a bona fide emergency braking maneuver on the street. If you don’t get that right (first time around, no practice runs) you might be injured or killed.

It turns out the average rider can only brake at about 60% of the bike’s capability, not quite test-rider numbers. If the rider locks the brakes on his way toward a left-turning pickup, the numbers are even worse. See what happens above when tire slip approaches 100% (lock-up)? Stopping power is reduced by about 20%. Skidding one or both of the tires is not a good evasive tactic, yet that’s what we’re seeing much of the time.

Not only does locking the tires reduce stopping power, it eliminates lateral stability of the tire. All the stickiness the tire has is being used up in sliding, so if the locked tire wants to move to the left or right, it will. 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, a.k.a. “laying it down.” Very few people actually lay it down on purpose, it’s just a result of improper braking. If you lock the rear tire, it generally won’t result in any sudden loss of control, but the same isn’t true for the front. Locking the front usually results in the motorcycle hitting the deck in one second or less. Then the motorcycle is sliding across the ground, heading in whatever direction it was initially heading, and slowing at a rate of only about 60% of what a good braking maneuver will accomplish. Again, not a good evasive tactic. I’d opt for a controlled stop via braking.

Like I said, the average rider can only exploit 60% of the bike’s stopping power. I suspect that sounds a little low to you, but there are six solid studies that show the average rider can only hit a deceleration rate of 0.64 g’s when most bikes are capable of 1.0 to 1.1 g’s [2-7]. Those studies analyzed 1,200+ braking tests from over 600 different riders. These tests were conducted in controlled environments, and in all but 50 of them, they knew exactly what they were supposed to do. No potential injury, no potential death, no uncertainty in the appropriate response (do I brake, swerve, accelerate, etc.). I wonder how these numbers might change in the face of danger? Even in this controlled environment though, locking occurred often [3]. Again, locking the tires reduces stopping power, which is not a good thing when you’re trying to avoid hitting a two-ton pickup. The slower the impact speed the better, and 0 mph is best.

So, what happens when we introduce ABS? Vavryn and his crew examined that, investigating the behavior of 181 riders during 800 tests [4]. The riders performed two tests on their own motorcycle, and then two runs on a motorcycle equipped with ABS. One of the ABS test-bikes was a standard BMW, while the other was a scooter equipped with linked ABS. 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%, despite the fact that the riders were now on an unfamiliar machine. Overall, 85% of the subjects improved braking with the ABS motorcycles, and the novice riders achieved braking rates almost equal to experienced riders when operating the ABS machines. That’s a nice perk. As with many things motorcycle, confidence is key, and ABS seems to give riders a boost in that department.

Let’s put that in perspective. What’s the difference between braking at 0.80 g’s compared to braking at 0.64 g’s? Let’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. How fast are you going when you hit the left-turner now? Over 20 mph. Ouch. That’s the difference between going home riled up and swearing, and getting toted away in an ambulance, or worse.

Let’s step out of the micro and jump into the macro, because a study has recently been conducted that directly shows how much ABS helps riders avoid collisions [8]. In 2013, the Insurance Institute for Highway Safety published an in-depth study analyzing insurance claims for over 425,000 motorcycles; 91,823 of which were equipped with ABS and 12,675 of which were equipped with ABS and some sort of combined braking system (CBS), where both brakes are actuated using one lever. The bikes involved in the study varied from Honda Gold Wings to Kawasaki ZX-10Rs. Ultimately, motorcycles equipped with ABS saw a 20% reduction in collision frequency and those equipped with ABS and CBS saw a massive 31% reduction. Relative to fatal motorcycle collisions, ABS alone was associated with a 31% reduction [9].

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 brake with the finesse that is necessary to fully exploit the motorcycle’s ability when presented with a life-threatening hazard. Fortunately, there’s a system that can ensure I don’t lock a tire and lose control, decrease my stopping distance, and reduce my chances of being involved in a collision. So, that’s why I decide to buy a street-bike with ABS, and I highly recommend you do the same.