How Does Motorcycle Traction Control Work?

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How Does Motorcycle Traction Control Work?

Traction Control is the latest must-have on performance motorcycles, helping manage unprecedentedly huge horsepower numbers and adding safety in poor conditions. But how does motorcycle traction control work? Here’s a detailed explanation that anyone can understand.

Traction control was brought about in an attempt to curtail vehicles from exceeding their available traction. As with many technologies such as fuel-injection and antilock brakes, traction control is finally coming under the umbrella of tech to expect with a new motorcycle purchase. At present we’re seeing the technology follow the same trickledown effect from top race classes and race replicas down to the smallest budget oriented models. It’s a boon for motorcyclists of any distinction. But how does it actually work?

Without Motorcycle Traction Control
Without Motorcycle Traction Control

Our motorcycles have just a few square inches of contact to the road surface via our tires. Road surfaces can be wet, dry, sandy, hot, cold, freshly paved, cracked, uneven, slippery, or covered in leaves, fluids, or foreign materials that change the amount of traction our tires can utilize. Our tires can be old or new (with traces of slippery mold release agents), improperly inflated, or have uneven wear. Traction control helps to mitigate loss of traction from all of these factors, as well as excessive application of throttle or other input errors on the part of the rider. No matter what the circumstances, the common denominator among all of these factors is a difference between rear wheel speed and front wheel speed.

So how do we get an accurate sense of wheel speeds? We repurpose the ABS sensors that are already monitoring them. We’re specifically concerned with the rear wheel speed in relation to the front. When the rear wheel is unable to maintain traction through its contact patch, it slides, and the rotation of the rear wheel no longer matches the rotation of the front wheel. The sensors relate this information to the bike’s ECU. Since the ECU controls fueling and engine speed, it already knows the amount of power the bike is delivering to the rear wheel. In some cases, it also registers throttle position, gear position and even lean angle. With the combination of wheel speed sensor data and engine speed data, the ECU can make a determination on available traction, and trigger one or more responses (which varies between motorcycle manufacturers).

Motorcycle Traction Control
Motorcycle Traction Control

At least one of three things will happen as the ECU attempts to prevent rear wheel slip : 1) retard the ignition timing, 2) skip fuel injection on a single cylinder, thereby intentionally creating a misfire, or 3) electronically adjust the throttle (assuming the bike is fitted with an electronic throttle). All of these events culminate in the same result, wherein engine output is modulated carefully so that traction is regained with smoothness and a maximum amount of efficiency. All the manufacturers choose the way the ECU intervenes differently. Aprilia and BMW TC retards ignition timing and electronically adjusts the throttle. Ducati TC retards ignition timing and uses cylinder misfires. Kawasaki TC only uses cylinder misfires. Yamaha TC uses all three, by retarding ignition timing, using cylinder misfires and adjust the throttle as needed.

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  • Andy Yun

    I know when my ABS brakes are working, but do I know when the APRC traction control is working? I ask because I don’t want to go from riding one with traction control to riding a motorcycle without TC and learn the hard way that I can’t ride the same way. Get my drift?

    • http://RideApart.com/ Wes Siler

      Ideally, you wouldn’t have bought a 180bhp streetfighter as your first big bike.

      But, you did, so if you notice a yellow light flashing on the dash (please keep looking ahead), that’s indicating TC is working. If you’re riding with it turned all the way up (please god, tell me you are), then you should definitely see that flashing yellow light every now and again. Go give it beans in 2nd gear and it’ll probably illuminate (please god, tell me you have wheelie control turned all the way up.

      • Stuki

        As much as I respect Keith Code; the mantra from the CSB marketing department that 200hp liter bikes are the safest and easiest to ride bikes out there now due to all the gizmos, even for beginning sport riders; isn’t really doing what seems to be your cause here any favors.

      • Piglet2010

        On the other hand, high-siding at the track can be a valuable learning experience.

    • ChrisMag100 .

      APRC is fairly mild in the way it behaves, except in very extreme circumstances. 95% of the time I’ve had it engage, all you notice is a mild reduction in power. The other 5%, it’s catching rear spin/sliding in the same way you would when riding dirt, by temporarily holding or slightly closing the throttle. Having ATC does not prevent you from spinning the rear – the system is designed to allow a specific amount of slip, depending on the level it’s set to.

      I can easily jump on a non-TC equipped 1000cc sport bike without any trouble, even after 2.5 years on my 2011 RSV4. You adapt to the characteristic of each bike through time and experience.

  • Jack Meoph

    Technological improvements like TC and ABS are one reason I try to buy a new MC every 5 years or so. Boredom is usually the other reason.

    • Braden

      Electronic gewgaws are half the reason I want new bikes. Skyhook, KTMs new Stability Control, even little things like wireless tire pressure monitors. I get excited just thinking about all the novelty gizmos to get.

  • John Wheeler

    you left out honda they were the first over 12 years ago traction control nothin new to RC -51 riders

  • Aaron Averett

    What do they mean by controlling traction with “cylinder misfires?” Does that really mean that just doesn’t fuel the cylinders every rotation, thus reducing power output?

    • Braden

      You’ve got it exactly right. If I remember right, earlier attempts dropped the spark instead of the fueling to create the intentional misfire, but dumping unspent fuel into the exhaust was bad for emissions.

  • Dave Day

    Did anyone else have a problem with the body positioning of the animated guy in the first video?

  • Lord Triumph

    I get all this but what’s still confusing is if a TC system is using the course spaced holes in the ABS ring which seems to be read by a simple magnet, how can the ECU gather enough pieces of data per second to make calculations for the TC in milliseconds?

    • Braden

      From what I’ve gathered even ABS sensors get about 50-60 “snapshots” of what’s going on per every rotation of the wheel. Upspec them to a slightly higher resolution sensor, get the ECU to interpolate between the data points, and I think you get enough data to process and respond to sudden changes down in the milliseconds. Either that or it’s magic.

    • Stuki

      The same way abs makes use of the same sensors to prevent the tires from breaking traction on the brakes. On the latest KTM adventure, the abs computer also takes lean angle into account, supposedly allowing you to just grab all the lever you want, even when leaned over on surfaces as unforgiving as cobblestone…. Sounds scary as heck to me, but one of the MC mags tested it, and once they managed to get past the fear, it actually did work….

  • Stuki

    All that’s missing now, is a servo in the steering head optimally steering into a slide…………

    • http://RideApart.com/ Wes Siler

      Actually, your bike will naturally steer into a slide in the appropriate amount for correction provided you let it. Just one more reason not to ride with stiff arms and a death grip.

  • octodad

    is there throttle by wire? fuel delivery controlled by microprocessor? this would allow greater control over wheel speed, especially when coupled w/ brake by wire using proportional solenoid calipers. do not like to mess with timing, and could engine misfiring have unwanted consequences? how about the new electric bikes? appears those motorcycles are already set up for TC.

    • Justin McClintock

      Yes, I know at least the Yamahas use throttle by wire (and have been for quite some time). I wouldn’t be at all surprised if others are now. And fuel deliver controlled by microprocessor is simply electronic fuel injection, which we’ve had for a LONG time now.

      As for brake by wire, now you’re talking about something with SERIOUS unintended consequences. The first time your thottle system fails because of a bad sensor, you pull in the clutch and grab the brakes. Even if the ABS screws up, the bike will still stop (and most ABS systems simply fail by eliminating the ABS from the loop, still allowing the brakes full normal function). But if you ad in brake by wire and it fails….well, you might just be screwed.

      As for engine timing, it’s only the spark timing they’re messing with, not the valve timing as it wouldn’t respond as quickly. Retarding spark timing (within reason) won’t hurt an engine at all. It’ll simply make less power.

      • octodad

        Mercedes and I believe Lexus have brake by wire. they can make it work in the real world, why not for motorcycles? I am just an alley mechanic, but the way you qualify alteration of timing and spark makes it more suspicious to me. TC looks like it is all about controlling wheel speed, electronic braking systems may be a more efficient method. in 1974 I installed computer brakes (ABS) on school buses. now 40 years later we are seeing ABS on motorcycles. WTF, this is life safety issue, did someone say ” that will not work on motorcycles, because…”

        • Justin McClintock

          BMW has brake by wire as well. In fact, they may have been the first (although it may have been Mercedes, not sure). Anyway, they’ve spent millions upon millions of dollars to create an incredibly complex braking system. Then they spent millions upon millions more simply to try to make it behave like a traditional system. In other words, they basically added complexity for complexity’s sake. They don’t necessarily work any better than any traditional system out there, they’re simply more complicated and have far more failure modes. Not to mention that it would be additional weight to a motorcycle.

          As for the, “that will not work on motorcycles because…”, well yes, that’s part of it. The original ABS systems were big and computing power was limited. Strapping 50 lbs. worth of gear to an E class Mercedes is negligible. Doing so to a motorcycle isn’t. Additionally, the dynamics of motorcycling handling and braking are far more complex than that of a car since it’s only got 2 wheels and can tip over. Shoot, until the mid 90′s cars with ABS weren’t even that common.

          And since you’re asking for ABS, you can get that without a fully electronic braking system. Plenty of cars (both of our Mazdas included) have traditional systems with ABS….as does every motorcycle equipped with ABS (of which there are quite a few now). It doesn’t have to be a fully electronic, brake-by-wire system or anything. (Then again, I just realized you’re probably well aware of that since you installed them on buses.) And some cars even use that system to help with traction control as well, while still maintaining a traditional master cylinder.

          • octodad

            there is a big show coming to my area soon. hope some tech guys have time to converse. I would ride old and home built bikes as a young man. now have a 2014 w/ a lot of safety features. when I gear up it is a new experience. feel more in control, and more secure on the scoot…

            • Justin McClintock

              I’ve got some questions about motorcycle ABS myself. I know in premise how it works. But I’m just curious about the mountings of things. Has it all gotten so small that it’s all on the bars for the front? Or does the front brake line run back to the chassis where the ABS module is? Although honestly, I could probably answer most of those questions with a stop into the dealership. Maybe I’m due….

  • HammSammich

    Thank you guys for this thorough explanation of the technology. I personally have no experience with traction control on motorcycles but as I’ve been looking for a new/second bike, I’ve been reading more about it. I realize that the various systems rely on different data sets and intervention methods, but I’m curious if any of the systems could potentially cause a high side in certain conditions?
    Additionally, would the lack of TC on a bike like the Street Triple R warrant looking at competitors?

    • http://RideApart.com/ Wes Siler

      TC has been pretty thoroughly developed. I don’t see an electronic Gremlin suddenly deciding to throw you off simply because ze Germans forgot to figure in data from damp roads or something.

      And yes, TC is a feature you should be looking for in new motorcycles. In the Street Triple’s case, it’s a great bike and none of the competition matches that greatness, TC or no.

  • http://RideApart.com/ Wes Siler

    You’ve ridden a bike with ABS, right? When you start it up, the ABS is in “calibration” mode and doesn’t turn on until you’ve travelled a little ways and gained a little speed (10mph or whatever). If it fails to turn on, a light just illuminates in your dash and you don’t have ABS brakes, it doesn’t prevent the bike from rolling along like normal. Same with TC.