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If your occupation is testing motorcycles there’s a certain measure of accepted risk that comes with the job. When cornering ABS (C-ABS) arrived a couple years ago, the general consensus among the motojournos was, Hey that’s awesome, we’ll take your word for it working as described, because no matter how professional we try to be, grabbing a fistful of front brake mid-corner to evaluate this new technology is a line few were willing to cross. Just thinking of the action conjures images of impacting asphalt at a rate approaching lightspeed.

Attending the International Driver & Rider Training Symposium provided Kevin Duke and I the opportunity to safely explore C-ABS and all the mid-corner braking performance the technology promises to deliver. The result? Confirmation that we were not being lied to, and an elevated respect for the engineers and test riders who perfect this technology prior to making it available to OEMs for inclusion on the latest and greatest two-wheelers.

With a KTM 1190 Adventure outfitted with Cedergrens’ Skidbike contraption, Duke and I set to the task of crashing. Repeatedly, we failed. Grabbing a fistful of brakes while leaned over with the C-ABS functioning resulted with a rapidly decelerating motorcycle, and – once the initial I-shouldn’t-be-doing-this gag reflex was muted – no drama. Switching off C-ABS and replicating the act resulted as you’d expect, with the front wheel washing away, but minus the crash due to Skidbike’s outriggers catching our falls.
Read more about the MO Tested: Cornering ABS at Motorcycle.com.
 

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Very interesting, but how many current bikes are equipped with C-ABS systems?

Most of the new bikes have ABS, but does this work in the corners like C-ABS or are they the same?

I have experienced some amazing emergency stops with ABS and am sure it has kept me from going down on wet surfaces.

Some new bikes also are equipped with traction control that helps in corners too. Some bikes like KTM SA, BMW GS1200 and Tiger 800 / 1200 EX have this. Some are only helping with rear wheel spin in different surfaces, but others actually help regulate power in the corners too.

Lots of good tech on bikes now! Good to know they actually work :)



J
 

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So does that mean that current ABS is only good on straight and no good on leans?
I'd go with 'Yes.' to be safe. It's not quite that cut and dried of course...

Firstly you can be pretty confident that anyone selling a bike with cornering ABS will trumpet it from the rooftops in the same way ABS was originally enthusiastically advertised when new. They are different and due to the additional cost of C-ABS I would say at this time a bike with only ABS listed in the spec is not hiding its light under a bushel but simply not equipped with C-ABS.

When you're leaning into a corner the tyres are undergoing increased stress and working harder then when you're rolling along upright because forces are acting along the lateral plane (centripetal/centrifugal movement relative to the arc you're describing as you go round the corner) and for this reason I'd expect the software at work in the C-ABS to be more sophisticated than with standard ABS. What I'm trying to say with that horrible car crash of words is that the more you're leaning then the less capacity the tyres have for braking because they're already using some of their reserves of grip for keeping the bike on the line you've asked for. And before the front or rear tyre actually locks up under braking you may find the bike's rear swings round to oversteer or the front begins to slide and you encounter understeer. The interactions between the front and the rear of the bike become more important mid corner under braking.

If you're riding bolt upright in a straight line then things are simpler. At it's crudest you could simply say when riding upright "If the wheels stop turning under braking but we were travelling above 10(?)mph the moment before then we're currently skidding: release the brakes for a fraction of a second, let the wheels spin up to a sensible speed again and then reapply the brakes". ABS can of course also respond if only one wheel suddenly stops turning and it doesn't just release the brake pressure but eases it off until the wheel or wheels pick up an appropriate speed again.

Cornering ABS is more refined because it reads the lean angle of the bike and factors in that angle when responding more intelligently to a loss of traction under braking. C-ABS systems vary I'm sure but as well as triggering the back brake to help out if the front wheel is struggling under braking (and vice versa) they can also monitor pitch, roll and lateral acceleration to understand in more detail how the bike's moving. (Graphic of pitch, roll and yaw here for non pilots!) For instance what happens to the rear tyre if the C-ABS eases off the brake pressure on the front tyre? Upright and rolling in a straight line not a lot might happen but when you're leaning over mid corner the change may be enough to cause the rear to grip substantially more and alter the line of the bike through the corner. Tricky stuff. All of these inputs are monitored by pretty complex software to give a more refined response to a squirrelly moment when you're leaning over and so you need more computing power as well as more sensors. Expensive stuff and therefore not included in standard ABS on bikes.

Bottom line? The further you're leaning over the harder standard ABS will find it to save your bacon and the more likely it is that cornering ABS will yield a better result. Laws of physics notwithstanding - sometimes you're just out of luck :)

Andy
 
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